Humidifier for a respiratory therapy device

ABSTRACT

A humidifier for humidification of air to be delivered to a patient&#39;s airways may include a humidification chamber, a reservoir and a water delivery mechanism. The humidification chamber may include a water retention feature such as a wick, a heating element for heating the humidification chamber, and an air flow baffle configured to promote humidification. The humidifier may be further configured to execute one or more algorithms, for example to determine a condition of the humidifier and/or to mitigate any detected faults. In some forms, the humidifier may also comprise algorithms for controlling one or more components of the humidifier.

1 CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/125,761, filed Sep. 13, 2016, now U.S. Pat. No. 10,518,061, which isthe U.S. national phase of International Application No.PCT/AU2015/050102 filed 13 Mar. 2015, which designated the U.S. andclaims priority to Australian Provisional Patent Application Nos. AU2014900869, filed Mar. 13, 2014, AU 2014901035, filed Mar. 24, 2014, andAU 2014904513, filed Nov. 11, 2014, the entire contents of each of whichare incorporated herein by reference.

2 BACKGROUND OF THE TECHNOLOGY 2.1 Field of the Technology

The present technology relates to one or more of the detection,diagnosis, treatment, prevention and amelioration of respiratory-relateddisorders. In particular, the present technology relates to medicaldevices or apparatus, and their use.

2.2 Description of the Related Art

2.2.1 Human Respiratory System

The respiratory system of the body facilitates gas exchange. The noseand mouth form the entrance to the airways of a patient.

The airways include a series of branching tubes, which become narrower,shorter and more numerous as they penetrate deeper into the lung. Theprime function of the lung is gas exchange, allowing oxygen to move fromthe air into the venous blood and carbon dioxide to move out. Thetrachea divides into right and left main bronchi, which further divideeventually into terminal bronchioles. The bronchi make up the conductingairways, and do not take part in gas exchange. Further divisions of theairways lead to the respiratory bronchioles, and eventually to thealveoli. The alveolated region of the lung is where the gas exchangetakes place, and is referred to as the respiratory zone. See“Respiratory Physiology”, by John B. West, Lippincott Williams &Wilkins, 9th edition published 2011.

A range of respiratory disorders exist.

Obstructive Sleep Apnea (OSA), a form of Sleep Disordered Breathing(SDB), is characterized by occlusion or obstruction of the upper airpassage during sleep. It results from a combination of an abnormallysmall upper airway and the normal loss of muscle tone in the region ofthe tongue, soft palate and posterior oropharyngeal wall during sleep.The condition causes the affected patient to stop breathing for periodstypically of 30 to 120 seconds duration, sometimes 200 to 300 times pernight. It often causes excessive daytime somnolence, and it may causecardiovascular disease and brain damage. The syndrome is a commondisorder, particularly in middle aged overweight males, although aperson affected may have no awareness of the problem. See U.S. Pat. No.4,944,310 (Sullivan).

Cheyne-Stokes Respiration (CSR) is a disorder of a patient's respiratorycontroller in which there are rhythmic alternating periods of waxing andwaning ventilation, causing repetitive de-oxygenation and re-oxygenationof the arterial blood. It is possible that CSR is harmful because of therepetitive hypoxia. In some patients CSR is associated with repetitivearousal from sleep, which causes severe sleep disruption, increasedsympathetic activity, and increased afterload. See U.S. Pat. No.6,532,959 (Berthon-Jones).

Obesity Hyperventilation Syndrome (OHS) is defined as the combination ofsevere obesity and awake chronic hypercapnia, in the absence of otherknown causes for hypoventilation. Symptoms include dyspnea, morningheadache and excessive daytime sleepiness.

Chronic Obstructive Pulmonary Disease (COPD) encompasses any of a groupof lower airway diseases that have certain characteristics in common.These include increased resistance to air movement, extended expiratoryphase of respiration, and loss of the normal elasticity of the lung.Examples of COPD are emphysema and chronic bronchitis. COPD is caused bychronic tobacco smoking (primary risk factor), occupational exposures,air pollution and genetic factors. Symptoms include: dyspnea onexertion, chronic cough and sputum production.

Neuromuscular Disease (NMD) is a broad term that encompasses manydiseases and ailments that impair the functioning of the muscles eitherdirectly via intrinsic muscle pathology, or indirectly via nervepathology. Some NMD patients are characterised by progressive muscularimpairment leading to loss of ambulation, being wheelchair-bound,swallowing difficulties, respiratory muscle weakness and, eventually,death from respiratory failure. Neuromuscular disorders can be dividedinto rapidly progressive and slowly progressive: (i) Rapidly progressivedisorders: Characterised by muscle impairment that worsens over monthsand results in death within a few years (e.g. Amyotrophic lateralsclerosis (ALS) and Duchenne muscular dystrophy (DMD) in teenagers);(ii) Variable or slowly progressive disorders: Characterised by muscleimpairment that worsens over years and only mildly reduces lifeexpectancy (e.g. Limb girdle, Facioscapulohumeral and Myotonic musculardystrophy). Symptoms of respiratory failure in NMD include: increasinggeneralised weakness, dysphagia, dyspnea on exertion and at rest,fatigue, sleepiness, morning headache, and difficulties withconcentration and mood changes.

Chest wall disorders are a group of thoracic deformities that result ininefficient coupling between the respiratory muscles and the thoraciccage. The disorders are usually characterised by a restrictive defectand share the potential of long term hypercapnic respiratory failure.Scoliosis and/or kyphoscoliosis may cause severe respiratory failure.Symptoms of respiratory failure include: dyspnea on exertion, peripheraloedema, orthopnea, repeated chest infections, morning headaches,fatigue, poor sleep quality and loss of appetite.

Otherwise healthy individuals may take advantage of systems and devicesto prevent respiratory disorders from arising.

2.2.2 Therapy

Nasal Continuous Positive Airway Pressure (CPAP) therapy has been usedto treat Obstructive Sleep Apnea (OSA). The hypothesis is thatcontinuous positive airway pressure acts as a pneumatic splint and mayprevent upper airway occlusion by pushing the soft palate and tongueforward and away from the posterior oropharyngeal wall.

Non-invasive ventilation (NIV) provides ventilatory support to a patientthrough the upper airways to assist the patient in taking a full breathand/or maintain adequate oxygen levels in the body by doing some or allof the work of breathing. The ventilatory support is provided via apatient interface. NIV has been used to treat CSR, OHS, COPD, MD andChest Wall disorders.

Invasive ventilation (IV) provides ventilatory support to patients thatare no longer able to effectively breathe themselves and is providedusing a tracheostomy tube.

Ventilators may control the timing and pressure of breaths pumped intothe patient and monitor the breaths taken by the patient. The methods ofcontrol and monitoring patients typically include volume-cycled andpressure-cycled methods. The volume-cycled methods may include amongothers, Pressure-Regulated Volume Control (PRVC), Volume Ventilation(VV), and Volume Controlled Continuous Mandatory Ventilation (VC-CMV)techniques. The pressure-cycled methods may involve, among others,Assist Control (AC), Synchronized Intermittent Mandatory Ventilation(SIMV), Controlled Mechanical Ventilation (CMV), Pressure SupportVentilation (PSV), Continuous Positive Airway Pressure (CPAP), orPositive End Expiratory Pressure (PEEP) techniques.

2.2.3 Systems

A system may comprise a Respiratory Therapy Device (RPT) device, an aircircuit, a humidifier, a patient interface, and data management.

2.2.4 Patient Interface

A patient interface may be used to interface respiratory equipment toits user, for example by providing a flow of air. The flow of air may beprovided via a mask to the nose and/or mouth, a tube to the mouth or atracheostomy tube to the trachea of the user. Depending upon the therapyto be applied, the patient interface may form a seal, e.g. with a faceregion of the patient, to facilitate the delivery of gas at a pressureat sufficient variance with ambient pressure to effect therapy, e.g. apositive pressure of about 10 cmH2O. For other forms of therapy, such asthe delivery of oxygen, the patient interface may not include a sealsufficient to facilitate delivery to the airways of a supply of gas at apositive pressure of about 10 cmH2O.

The design of a patient interface presents a number of challenges. Theface has a complex three-dimensional shape. The size and shape of nosesvaries considerably between individuals. Since the head includes bone,cartilage and soft tissue, different regions of the face responddifferently to mechanical forces. The jaw or mandible may move relativeto other bones of the skull. The whole head may move during the courseof a period of respiratory therapy.

As a consequence of these challenges, some masks suffer from being oneor more of obtrusive, aesthetically undesirable, costly, poorly fitting,difficult to use, and uncomfortable especially when worn for longperiods of time or when a patient is unfamiliar with a system. Forexample, masks designed solely for aviators, mask designed as part ofpersonal protection equipment (e.g. filter masks), SCUBA masks, or forthe administration of anaesthetics may be tolerable for their originalapplication, but nevertheless be undesirably uncomfortable to be wornfor extended periods of time, e.g. several hours. This is even more soif the mask is to be worn during sleep.

Nasal CPAP therapy is highly effective to treat certain respiratorydisorders, provided patients comply with therapy. If a mask isuncomfortable, or difficult to use a patient may not comply withtherapy. Since it is often recommended that a patient regularly washtheir mask, if a mask is difficult to clean (e.g. difficult to assembleor disassemble), patients may not clean their mask and this may impacton patient compliance.

While a mask for other applications (e.g. aviators) may not be suitablefor use in treating sleep disordered breathing, a mask designed for usein treating sleep disordered breathing may be suitable for otherapplications.

For these reasons, masks for delivery of nasal CPAP during sleep form adistinct field.

2.2.5 Respiratory Pressure Therapy (RPT) Device

Examples of RPT devices include ResMed's S9 AutoSet™ PAP device andResMed's Stellar™ 150 ventilator. RPT devices may comprise a pressuregenerator, such as a motor-driven blower or a compressed gas reservoir,and may be configured to supply a flow of air to the airway of apatient. In some cases, the flow of air may be supplied to the airway ofthe patient at positive pressure. The outlet of the RPT device isconnected via an air circuit to a patient interface such as thosedescribed above. In some cases, RPT devices have been known to bereferred to as flow generators.

RPT devices may include a pressure generator, an inlet filter, varioussensors and a microprocessor-based controller. The pressure generatormay include a servo-controlled motor, volute and an impeller. In somecases a brake for the motor may be implemented to more rapidly reducethe speed of the blower so as to overcome the inertia of the motor andimpeller. The braking can permit the blower to more rapidly achieve alower pressure condition in time for synchronization with exhalationdespite the inertia. In some cases the pressure generator may alsoinclude a valve capable of discharging generated air to atmosphere as ameans for altering the pressure delivered to the patient as analternative to motor speed control. The sensors may measure, amongstother things, motor speed, air flow rate and outlet pressure, such aswith a pressure transducer or the like. The controller may include datastorage capacity with or without integrated data retrieval and displayfunctions.

Table of noise output levels of prior devices (one specimen only,measured using test method specified in ISO3744 in CPAP mode at 10cmH₂O).

A-weighted sound Device name power level dB (A) Year (approx.) C-SeriesTango 31.9 2007 C-Series Tango with Humidifier 33.1 2007 S8 Escape II30.5 2005 S8 Escape II with H4i Humidifier 31.1 2005 S9 AutoSet 26.52010 S9 AutoSet with H5i Humidifier 28.6 2010

2.2.6 Humidifier

Delivery of a flow of air without humidification may cause drying ofairways. Medical humidifiers, or humidifiers for respiratory therapydevices, may be used to increase absolute humidity and/or temperature ofthe flow of air in relation to ambient air when required, for example,where the patient may be asleep or resting (e.g. at a hospital). As aresult, a medical humidifier may be small for bedside placement, and itmay be configured to only humidify and/or heat the flow of air deliveredto the patient without humidifying and/or heating the patient'ssurroundings. Room-based systems (e.g. a sauna, an air conditioner, anevaporative cooler), for example, may also humidify air that is breathedin by the patient, however they would also humidify and/or heat theentire room, which may cause discomfort to the occupants.

The use of a humidifier with a pressure generator or RPT device and thepatient interface produces humidified gas that minimizes drying of thenasal mucosa and increases patient airway comfort. In addition in coolerclimates, warm air applied generally to the face area in and about thepatient interface is more comfortable than cold air.

Respiratory humidifiers are available in many forms and may be astandalone device that is coupled to an RPT device via an air conduit,may be integrated with the RPT device, or may be configured to bedirectly coupled to the relevant RPT device. While known passivehumidifiers can provide some relief, generally a heated humidifier maybe used to provide sufficient humidity and temperature to the air sothat the patient will be comfortable. Humidifiers may comprise a waterreservoir or tub having a capacity of several hundred milliliters (ml),a heating element for heating the water in the reservoir, a control toenable the level of humidification to be varied, a gas inlet to receivegas from the RPT device, and a gas outlet adapted to be connected to anair circuit that delivers the humidified gas to the patient interface.

Heated passover humidification is one exemplary form of humidificationused with an RPT device. In such humidifiers the heating element may beincorporated in a heater plate which sits under, and is in thermalcontact with, the water tub. Thus, heat is transferred from the heaterplate to the water reservoir primarily by conduction. The air flow fromthe RPT device passes over the heated water in the water tub resultingin water vapour being taken up by the air flow. The ResMed H4i™ and H5i™Humidifiers are examples of such heated passover humidifiers that areused in combination with ResMed S8 and S9 RPT devices respectively.

Other humidifiers may also be used such as a bubble or diffuserhumidifier or a jet humidifier. In a bubble or diffuser humidifier theair is conducted below the surface of the water and allowed to bubbleback to the top. A jet humidifier produces an aerosol of water andbaffles or filters may be used so that the particles are either removedor evaporated before leaving the humidifier.

An alternative form of humidification is provided by the ResMedHumiCare™ D900 humidifier that uses a CounterStream™ technology thatdirects the air flow over a large surface area in a first directionwhilst supplying heated water to the large surface area in a secondopposite direction. The ResMed HumiCare™ D900 humidifier may be usedwith a range of invasive and non-invasive ventilators.

One example of a prior art humidifier 5000 is shown in FIGS. 6A and 6B,and comprises a reservoir 5110 to retain a volume of liquid (e.g.water), an air inlet 5002 to receive a flow of air, and an air outlet5004 to deliver a humidified flow of air. In some forms, as shown inFIG. 6A and FIG. 6B, an inlet and an outlet of the reservoir 5110 may bethe air inlet 5002 and the air outlet 5004 respectively. The reservoir5110 may be a removable component of the humidifier 5000. The humidifier5000 may further comprise a humidifier dock 5130, which may be adaptedto receive the reservoir 5110 and comprise a heating element 5220. Thereservoir 5110 may comprise a conductive plate 5120 configured to allowefficient transfer of heat from the heating element 5220 to the volumeof liquid in the reservoir 5110.

Thus, in such a form, the reservoir 5110 contains the entire volume ofwater to be used to humidify the flow of air, and receives the flow ofair to pass over the water and delivers the humidified flow of air.Accordingly, such a humidifier configuration presents a number ofchallenges, including: risk of spillage of the volume of water (e.g.into the RPT device or to the patient), achieving adequatehumidification output, high thermal mass of the volume of water andchanges to thermal mass according to changes in water volume present inthe reservoir 5110. Due to these challenges, many prior art humidifiersmay suffer from one or more of: long warm-up time and cool-down time,slow response time (e.g. to a change in desired humidification output),change to response time throughout a therapy session and large size. Thelarge size may manifest itself in terms of volume and/or footprint (i.e.surface area covered by the humidifier, or effectively covered by thehumidifier as to become inaccessible), which may make the humidifierless suited for placement on a bedside table for example. A humidifier5000 according to the present technology seeks to improve upon, orameliorate, one or more of the above characteristics.

3 BRIEF SUMMARY OF THE TECHNOLOGY

The present technology is directed towards providing medical devicesused in the diagnosis, amelioration, treatment, or prevention ofrespiratory disorders having one or more of improved comfort, cost,efficacy, ease of use and manufacturability.

A first aspect of the present technology relates to an apparatus used inthe diagnosis, amelioration, treatment or prevention of a respiratorydisorder.

Another aspect of the present technology relates to methods used in thediagnosis, amelioration, treatment or prevention of a respiratorydisorder.

One aspect of the present technology relates to a humidifier forincreasing an absolute humidity of a flow of air to be delivered to apatient's airways by a respiratory therapy device. The humidifier maycomprise a reservoir configured to retain a first volume of water, ahumidifier chamber comprising an air inlet configured to receive theflow of air from a pressure device, an air outlet configured to deliverthe flow of air to a patient interface from the humidifier chamber withadded humidity, a flow path for the flow of air through the humidifierchamber, a humidifier wick configured to retain a second volume of waterand the humidifier wick having a profiled shape to substantially encloseat least a portion of the flow path for the flow of air in an axialdirection of the flow path, a heating element, and an air flow baffleconfigured to lengthen the flow path for the flow of air through thehumidifier chamber, and a delivery mechanism configured to deliver aflow of water from the reservoir to the humidifier wick, wherein theheating element is configured to heat the humidifier wick to vaporisethe second volume of water to add absolute humidity to the flow of airand the humidifier wick is removable from the humidifier chamber.

According to another aspect of the present technology, the humidifierwick may be anisotropically configured.

According to another aspect of the present technology, the humidifierwick may be further configured so that a rate of wicking is greater in afirst direction than in a second direction.

According to another aspect of the present technology, the seconddirection may be a direction of the flow of air.

According to another aspect of the present technology, the path enclosedby the humidifier wick may be substantially cylindrical.

According to another aspect of the present technology, the humidifierwick may comprise one or more of: a corrugated, a dimpled, a perforated,a porous, a woven, a knitted, a textured, and a sintered surface.

According to another aspect of the present technology, the humidifierwick may comprise one or more of: paper, hydrophilic fibres, andcellulose fibres.

According to another aspect of the present technology, the humidifierwick may comprise a substrate for the heating element.

According to another aspect of the present technology, the humidifierwick may be configured to retain between 2-30 g of water.

According to another aspect of the present technology, the humidifierwick may comprise a heated region and an unheated region.

According to another aspect of the present technology, the unheatedregion may comprise an upstream unheated region located upstream of theheated region.

According to another aspect of the present technology, the upstreamunheated region may comprise a faster wicking rate than the heatedregion.

According to another aspect of the present technology, a length of theupstream unheated region may be between approximately 5%-approximately20% of the heated region.

According to another aspect of the present technology, the unheatedregion may comprise a downstream unheated region located downstream ofthe heated region.

According to another aspect of the present technology, a length of thedownstream unheated region may be between approximately20%-approximately 40% of the heated region.

According to another aspect of the present technology, the humidifierwick may be coupled to a frame.

According to another aspect of the present technology, the frame may beconfigured to be removably coupled to the humidifier chamber.

According to another aspect of the present technology, the frame may beconfigured to be removed from an exterior of the humidifier.

According to another aspect of the present technology, the frame maycomprise a grip surface.

According to another aspect of the present technology, the frame may beconfigured to promote thermal contact between the humidifier wick andthe heating element.

According to another aspect of the present technology, the frame mayfurther comprise the air flow baffle.

According to another aspect of the present technology, the lengthenedpath may be helical.

According to another aspect of the present technology, the heatingelement may comprise a resistive electrical track.

According to another aspect of the present technology, the resistiveelectrical track may be disposed on a circuit board.

According to another aspect of the present technology, the circuit boardmay be a flexible circuit board.

According to another aspect of the present technology, the resistiveelectrical track may comprise one or more strands of resistive wire.

According to another aspect of the present technology, the one or morestrands of resistive wire may form a plurality of loops around a surfaceof the humidifier chamber.

According to another aspect of the present technology, the heatingelement may further comprise an adhesive for securing the plurality ofloops.

According to another aspect of the present technology, the deliverymechanism may be configured to deliver the flow of water to thehumidifier wick through a plurality of fluid connections.

According to another aspect of the present technology, the deliverymechanism may be fluidly connected to the humidifier wick via apre-delivery chamber.

According to another aspect of the present technology, at least one ofthe fluid connections may be a valve.

According to another aspect of the present technology, the deliverymechanism may comprise a pump.

According to another aspect of the present technology, the humidifiermay further comprise one or more temperature sensors configured tomeasure one or more temperatures at the humidifier wick.

According to another aspect of the present technology, a plurality oftemperature sensors may be located along a direction of the flow of air.

Another aspect of the present technology may further comprise a sensorconfigured to indicate a saturation condition of the humidifier wick.

According to another aspect of the present technology, a temperaturesensor may be located at a periphery of the humidifier wick furthestfrom a water feed inlet to indicate the saturation condition.

Another aspect of the present technology may further comprise acontroller configured to stop or slow delivery by the delivery mechanismupon indication of the saturation condition.

One aspect of the present technology relates to a humidifier chamber fora humidifier for increasing an absolute humidity of a flow of air to bedelivered to a patient's airways by a respiratory therapy device. Thehumidifier chamber may comprise an air inlet configured to receive theflow of air from a pressure device, an air outlet configured to deliverthe flow of air to a patient interface from the humidifier chamber withadded humidity, a flow path through the humidifier chamber for the flowof air, and, a humidifier wick configured to retain a volume of waterand the humidifier wick having a profiled shape to substantially encloseat least a portion of the flow path for the flow of air in an axialdirection of the flow path.

According to another aspect of the present technology, the humidifierwick may be anisotropically configured.

According to another aspect of the present technology, the humidifierwick may be further configured so that a rate of wicking is greater in afirst direction than in a second direction.

According to another aspect of the present technology, the seconddirection may be a direction of the flow of air.

According to another aspect of the present technology, the path enclosedby the humidifier wick may be substantially cylindrical.

According to another aspect of the present technology, the humidifierwick may comprise one or more of: a corrugated, a dimpled, a perforated,a porous, a woven, a knitted, a textured, and a sintered surface.

According to another aspect of the present technology, the humidifierwick may comprise one or more of: paper, hydrophilic fibres, andcellulose fibres.

According to another aspect of the present technology, the humidifierchamber may comprise a heating element.

According to another aspect of the present technology, the humidifierwick may comprise a substrate for the heating element.

According to another aspect of the present technology, the humidifierwick may be configured to retain between 2-30 g of water.

According to another aspect of the present technology, the humidifierwick may comprise a heated region and an unheated region.

According to another aspect of the present technology, the unheatedregion may comprise an upstream unheated region located upstream of theheated region.

According to another aspect of the present technology, the upstreamunheated region may comprise a faster wicking rate than the heatedregion.

According to another aspect of the present technology, a length of theupstream unheated region may be between approximately 5%-approximately20% of the heated region.

According to another aspect of the present technology, the unheatedregion may comprise a downstream unheated region located downstream ofthe heated region.

According to another aspect of the present technology, a length of thedownstream unheated region may be between approximately20%-approximately 40% of the heated region.

According to another aspect of the present technology, the humidifierwick may be coupled to a frame.

According to another aspect of the present technology, the frame may beconfigured to be removably coupled to the humidifier chamber.

According to another aspect of the present technology, the frame may beconfigured to be removed from an exterior of the humidifier.

According to another aspect of the present technology, the frame maycomprise a grip surface.

According to another aspect of the present technology, the frame may beconfigured to promote thermal contact between the humidifier wick andthe heating element.

According to another aspect of the present technology, the frame mayfurther comprise an air flow baffle to lengthen the flow path.

According to another aspect of the present technology, the lengthenedpath may be helical.

According to another aspect of the present technology, the heatingelement may comprise a resistive electrical track.

According to another aspect of the present technology, the resistiveelectrical track may be disposed on a circuit board.

According to another aspect of the present technology, the circuit boardmay be a flexible circuit board.

According to another aspect of the present technology, the resistiveelectrical track may comprise one or more strands of resistive wire

According to another aspect of the present technology, the one or morestrands of resistive wire may form a plurality of loops around a surfaceof the humidifier chamber.

According to another aspect of the present technology, the heatingelement may further comprise an adhesive for securing the plurality ofloops.

Another aspect of the present technology may further comprise one ormore temperature sensors configured to measure one or more temperaturesat the humidifier wick.

According to another aspect of the present technology, a plurality oftemperature sensors may be located along the flow path of the flow ofair.

Another aspect of the present technology may further comprise a sensorconfigured to indicate a saturation condition of the humidifier wick.

According to another aspect of the present technology, a temperaturesensor may be located at a periphery of the humidifier wick furthestfrom a water feed inlet to indicate the saturation condition.

One aspect of the present technology relates to a method of determiningsuitability of a humidifier wick of a humidifier, e.g., a medicalhumidifier. The humidifier may comprise the humidifier wick and acontroller configured to receive one more signals and/or generate one ormore signals, and the humidifier wick may be configured to retain avolume of water. The method may comprise determining a set of inputvalues with a controller, wherein the set of input values are indicativeof a condition of a humidifier wick and the set of input values areprovided to the controller by at least one of user input, at least onesensor, and a memory device, determining, based on the set of inputvalues and a set of reference values, a condition set of the humidifierwick with the controller, and generating a signal with the controllerbased on the determined condition set to indicate a suitability of thehumidifier wick for use in the humidifier.

According to another aspect of the present technology, the set of inputvalues may comprise one or more of: wick type data, wick usage data, andmeasured wick condition data.

According to another aspect of the present technology, when the set ofinput values comprises the wick type data, the wick type data maycomprise one or more of: wick model, date of manufacture, wick material,wick construction, wick dimensions, and initial water capacity.

According to another aspect of the present technology, when the set ofinput values comprises the wick usage data, the wick usage data maycomprise one or more of: date of last replacement, time of use, quantityof water evaporated using the humidifier wick, and number of times thatthe humidifier wick has been washed.

According to another aspect of the present technology, when the set ofinput values comprises the measured wick condition data, the measuredwick condition data may comprise one or more of: a measured temperature,a water capacity, and a water content.

According to another aspect of the present technology, the condition setmay comprise one or more of: a water capacity, a water content, and aremaining useful life.

According to another aspect of the present technology, the set ofreference values may comprise a temperature.

According to another aspect of the present technology, the set ofreference values may comprise a temperature gradient.

According to another aspect of the present technology, the set ofreference values may comprise a look-up table.

According to another aspect of the present technology, the method mayfurther comprise communicating to a user the suitability of thehumidifier wick with a visual and/or audible communication device inresponse to the signal generated by the controller.

One aspect of the present technology relates to a method of determininga water content of a humidifier wick of a humidifier, e.g., a medicalhumidifier. The humidifier may comprise the humidifier wick and acontroller configured to receive one more signals and/or generate one ormore signals, and the humidifier wick may be configured to retain avolume of water. The method may comprise providing a first temperaturesensor in thermal contact with a first region of the humidifier wick anda second temperature sensor in thermal contact with a second region ofthe humidifier wick, applying a heat input to the humidifier wick, e.g.,with a heating element, measuring a measured temperature set with thefirst temperature sensor and the second temperature sensor, determininga predicted temperature set at the first temperature sensor and thesecond temperature sensor, e.g., with a controller, and determining awater content of the humidifier wick based on a comparison of themeasured temperature set received from the first temperature sensor andthe second temperature sensor and the predicted temperature set.

According to another aspect of the present technology, the predictedtemperature set may be determined based on one or more of a water flowrate to the humidifier wick and a rate of the heat input.

According to another aspect of the present technology, the firsttemperature sensor may be located at or near a periphery of thehumidifier wick.

According to another aspect of the present technology, the firsttemperature sensor may be located at a periphery of the humidifier wickfurthest from a water feed inlet to the humidifier wick.

According to another aspect of the present technology, the comparisonmay determine whether a temperature of the measured temperature set isoutside of a threshold range of a corresponding temperature of thepredicted temperature set.

One aspect of the present technology relates to a method of detectingoccurrence of condensation in a flow path for a flow of air delivered bya humidifier, e.g., a medical humidifier. The method may comprisedetermining a first measure of a first property of the flow of air witha first sensor located in the flow path, determining a reference valueof the first property of the flow of air with a second sensor located inthe flow path, comparing the first measure with the reference value witha controller in communication with the first sensor and the secondsensor, determining whether condensation has occurred in the flow pathbased on the comparison with the controller, and generating a signalwith the controller indicating whether condensation has occurred in theflow path.

According to another aspect of the present technology, an occurrence ofcondensation may be determined with the controller upon a decrease inthe first property from the reference value to the first measure.

According to another aspect of the present technology, the decrease inthe first property from the reference value to the first measure may beabove a predetermined threshold.

According to another aspect of the present technology, the referencevalue may be a second measure of the first property.

According to another aspect of the present technology, the secondmeasure may be determined upstream of the first measure.

According to another aspect of the present technology, the referencevalue may be a prediction of the first property of the flow of air.

According to another aspect of the present technology, the predictionmay be determined based on a steady-state condition.

According to another aspect of the present technology, the predictionmay be determined based on one or more of: a pressure of the flow ofair, a flow rate of the flow of air, an ambient temperature, an ambienthumidity, an ambient pressure, a rate of heat transfer to the flow ofair, and a rate of heat transfer between the flow of air and theambient.

According to another aspect of the present technology, the firstproperty of the flow of air is humidity, temperature, or rate of changeof the temperature.

According to another aspect of the present technology, the predictionmay be determined based on a steady-state condition.

One aspect of the present technology is directed to a method forcontrolling a location and/or a rate of foreign matter build-up on ahumidifier wick of a humidifier. The humidifier may comprising thehumidifier wick, a heating element to apply heat to the humidifier wick,a water delivery mechanism to deliver water to the humidifier wick, anda controller configured to receive one more signals and/or generate oneor more signals, and the humidifier wick being configured to retain avolume of water. The method may comprise controlling a location and/or apattern of a water boundary on the humidifier wick of the humidifier byvarying, with the controller, at least one of: a heat output from theheating element onto the humidifier wick; a water flow rate from thewater delivery mechanism onto the humidifier wick; and a waterdistribution pattern within the humidifier wick by adjusting the heatoutput from the heating element and/or the water flow rate from thewater delivery, wherein controlling the location and/or the pattern ofthe water boundary causes foreign matter to build up at a predeterminedregion of the humidifier wick based on the location and/or the patternof the water boundary.

According to another aspect of the present technology, the method mayfurther comprise detecting a foreign matter content of the water with asensor; and determining a quality of the water with the controller basedon the foreign matter content detected by the sensor.

According to another aspect of the present technology, detecting theforeign matter content of the water with the sensor may further comprisemeasuring a conductivity of the water with the sensor.

According to another aspect of the present technology, detecting theforeign matter content of the water with the sensor may further comprisemeasuring resistivity of the water with electrodes in contact with thewater.

According to another aspect of the present technology, the electrodesmay be located in the humidifier wick and the water contained in thehumidifier wick, and the resistivity measured by the electrodes may bedirectly correlated to a level of foreign matter build-up in thehumidifier wick.

According to another aspect of the present technology, if the water flowrate from the water delivery mechanism is varied, then the water flowrate may be varied between a minimum water flow and a maximum water flowrate.

According to another aspect of the present technology, the water flowrate may be varied linearly or sinusoidally.

According to another aspect of the present technology, if the locationof the water boundary is controlled, then the location of the waterboundary may be varied in a reciprocating motion such that the waterboundary moves between at least a first location and a second location.

According to another aspect of the present technology, if the heatoutput from the heating element onto the humidifier wick is varied, thenthe heat output may be varied between a minimum heat output and amaximum heat output.

According to another aspect of the present technology, the heat outputmay be varied linearly or sinusoidally.

Of course, portions of the aspects may form sub-aspects of the presenttechnology. Also, various ones of the sub-aspects and/or aspects may becombined in various manners and also constitute additional aspects orsub-aspects of the present technology.

Other features of the technology will be apparent from consideration ofthe information contained in the following detailed description,abstract, drawings and claims.

4 BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The present technology is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings, in whichlike reference numerals refer to similar elements including:

4.1 Treatment Systems

FIG. 1A shows a system including a patient 1000 wearing a patientinterface 3000, in the form of a nasal pillows, receiving a supply ofair at positive pressure from an RPT device 4000. Air from the RPTdevice is humidified in a humidifier 5000, and passes along an aircircuit 4170 to the patient 1000, a bed partner 1100 is also shown.

FIG. 1B shows a system including a patient 1000 wearing a patientinterface 3000, in the form of a nasal mask, receiving a supply of airat positive pressure from an RPT device 4000. Air from the RPT device ishumidified in a humidifier 5000, and passes along an air circuit 4170 tothe patient 1000.

FIG. 1C shows a system including a patient 1000 wearing a patientinterface 3000, in the form of a full-face mask, receiving a supply ofair at positive pressure from an RPT device 4000. Air from the RPTdevice is humidified in a humidifier 5000, and passes along an aircircuit 4170 to the patient 1000.

4.2 Therapy

4.2.1 Respiratory System

FIG. 2A shows an overview of a human respiratory system including thenasal and oral cavities, the larynx, vocal folds, oesophagus, trachea,bronchus, lung, alveolar sacs, heart, and diaphragm.

FIG. 2B shows a view of a human upper airway including the nasal cavity,nasal bone, lateral nasal cartilage, greater alar cartilage, nostril,lip superior, lip inferior, larynx, hard palate, soft palate,oropharynx, tongue, epiglottis, vocal folds, oesophagus, and trachea.

4.3 Patient Interface

FIG. 3 shows a patient interface 3000 in the form of a nasal mask inaccordance with one form of the present technology.

4.4 RPT Device

FIG. 4A shows an exploded view of an RPT device 4000 in accordance withone form of the present technology.

FIG. 4B shows a schematic diagram of the pneumatic circuit of an RPTdevice 4000 in accordance with one form of the present technology. Thedirections of upstream and downstream are indicated.

FIG. 4C shows a schematic diagram of the electrical components of an RPTdevice 4000 in accordance with one aspect of the present technology.

4.5 Breathing Waveforms

FIG. 5 shows a model typical breath waveform of a person while sleeping.The horizontal axis is time, and the vertical axis is respiratory flow.While the values may vary, a typical breath may have the followingapproximate values: tidal volume, Vt, 0.5 L, inhalation time, Ti, 1.6 s,peak inspiratory flow, Qpeak, 0.4 L/s, exhalation time, Te, 2.4 s, peakexpiratory flow, Qpeak, −0.5 L/s. The total duration of the breath,Ttot, is about 4 s. The person typically breathes at a rate of about 15breaths per minute (BPM), with Ventilation, Vent, about 7.5 L/minute. Atypical duty cycle, the ratio of Ti to Ttot is about 40%.

4.6 Humidifier

FIG. 6A shows one form of a prior art humidifier.

FIG. 6B shows the prior art humidifier of FIG. 6A, showing a reservoir5110 removed from a humidifier dock 5130.

FIG. 7 shows a perspective view of a humidifier 5000 according to oneaspect of the present technology.

FIG. 8 shows a schematic view of the humidifier of FIG. 7 furthercomprising a water delivery mechanism 5150 and a reservoir 5110.

FIG. 9A shows a cross-section view in elevation of the humidifier ofFIG. 7 .

FIG. 9B shows a cross-section view in elevation of a humidifier 5000according to an aspect of the present technology.

FIG. 10 shows an exploded perspective view of a portion of thehumidifier 5000 of FIG. 7 showing a humidifier wick 5230 and a wickframe 5232.

FIG. 11 shows a perspective view of one form of a heating element 5220for a humidifier according to the present technology, the heatingelement comprising multiple heating zones.

FIG. 12 shows a cross-section view in elevation of a humidifiercomprising a humidifier wick 5230 having multiple layers according to anaspect of the present technology.

FIG. 13 shows a perspective view of a humidifier wick 5230 according toan aspect of the present technology, the humidifier wick comprising acorrugated inner surface.

FIGS. 14A and 14B show cross-section views in elevation of a humidifier5000 showing a dry region 5230_D and a wet region 5230_W of thehumidifier wick 5230 according to an aspect of the present technology.

FIGS. 15A and 15B show cross-section views in elevation of a humidifier5000 including an arrangement of multiple humidifier transducersaccording to an aspect of the present technology.

FIG. 16 shows a cross-section view in elevation of a humidifierincluding a temperature sensor 5514_5 according to a further aspect ofthe present technology.

FIG. 17 shows an example of a relationship between a power output of aheating element and the humidity added to the flow of air by thehumidifier.

FIG. 18 shows an example of a relationship between a temperature of aheating element and the humidity added to the flow of air by thehumidifier.

FIG. 19 shows an example of a relationship between a power output of aheating element and the humidity added to the flow of air by thehumidifier at various air flow rates.

FIG. 20 shows a perspective view of a humidifier 5000 according to oneaspect of the present technology, wherein the heating element 5220comprises resistive wires.

FIG. 21 shows a representation of example humidifier algorithms 5600according to one aspect of the present technology.

FIG. 22 shows a flowchart of an example algorithm 5610A of a wickcondition determination algorithm according to one aspect of the presenttechnology.

FIG. 23 shows a flowchart of another example algorithm 5610B of a wickcondition determination algorithm according to one aspect of the presenttechnology.

FIG. 24 shows a flowchart of another example algorithm 5610C of a wickcondition determination algorithm according to one aspect of the presenttechnology.

FIG. 25 shows a flowchart of an example algorithm 5620A of aplausibility check algorithm according to one aspect of the presenttechnology.

FIG. 26 shows a representation of an example respiratory treatmentsystem comprising an RPT device 4000, a humidifier 5000 and a patientinterface 3000 according to one aspect of the present technology.

FIG. 27 shows a representation of an example respiratory treatmentsystem comprising an RPT device 4000, a humidifier 5000 and a patientinterface 3000 according to one aspect of the present technology.

FIG. 28 shows a representation of an example respiratory treatmentsystem comprising an RPT device 4000, a humidifier 5000 and a patientinterface 3000 according to one aspect of the present technology.

FIG. 29 shows an exemplary graph correlating a temperature change with apower output of a heating element.

FIG. 30A shows an exemplary graph correlating a power applied by aheating element correlated with time.

FIG. 30B shows another exemplary graph correlating a power applied by aheating element correlated with time.

FIG. 31 shows a cross-section view in elevation of a humidifier 5000including pre-delivery chamber according to an aspect of the presenttechnology.

FIG. 32 shows a cross-section view in elevation of a humidifier 5000including a humidifier wick located towards a centre of the humidifieraccording to an aspect of the present technology.

FIG. 33 shows a cross-section view in elevation of a humidifier 5000including air flow trip elements according to an aspect of the presenttechnology.

FIG. 34 shows a cross-section view in elevation of a humidifier 5000including an upstream unheated region of the wick, a heated region ofthe wick and a downstream unheated region of the wick according to anaspect of the present technology.

5 DETAILED DESCRIPTION OF EXAMPLES OF THE TECHNOLOGY

Before the present technology is described in further detail, it is tobe understood that the technology is not limited to the particularexamples described herein, which may vary. It is also to be understoodthat the terminology used in this disclosure is for the purpose ofdescribing only the particular examples discussed herein, and is notintended to be limiting.

The following description is provided in relation to various exampleswhich may share one or more common characteristics and/or features. Itis to be understood that one or more features of any one example may becombinable with one or more features of another example or otherexamples. In addition, any single feature or combination of features inany of the examples may constitute a further example.

5.1 TREATMENT SYSTEMS

In one form, the present technology comprises a system for treating arespiratory disorder. For example, a system may comprise an RPT device4000, a humidifier 5000, an air circuit 4170 and a patient interface3000.

5.2 THERAPY

In one form, the present technology comprises a method for treating arespiratory disorder comprising the step of applying positive pressureto the entrance of the airways of a patient 1000.

5.2.1 Nasal CPAP for OSA

In one form, the present technology comprises a method of treatingObstructive Sleep Apnea in a patient by applying nasal continuouspositive airway pressure to the patient.

In certain examples of the present technology, a supply of air atpositive pressure is provided to the nasal passages of the patient viaone or both nares.

5.3 PATIENT INTERFACE 3000

A non-invasive patient interface 3000 in accordance with one aspect ofthe present technology comprises the following functional aspects (e.g.as shown in FIG. 3 ): a seal-forming structure 3100, a plenum chamber3200, a positioning and stabilising structure 3300, and a connectionport 3600 for connection to air circuit 4170. The patient interface 3000may further comprise a forehead support 3700 in some forms, such as thatshown in FIG. 3 . In some forms, a functional aspect may be provided byone or more physical components. In some forms, one physical componentmay provide one or more functional aspects. In use the seal-formingstructure 3100 is arranged to surround an entrance to the airways of thepatient so as to facilitate the supply of air at positive pressure tothe airways.

In one form, the patient interface 3000 includes a vent 3400 constructedand arranged to allow for the washout of exhaled carbon dioxide.

One form of vent 3400 in accordance with the present technologycomprises a plurality of holes, for example, about 20 to about 80 holes,or about 40 to about 60 holes, or about 45 to about 55 holes.

The vent 3400 may be located in the plenum chamber 3200. Alternatively,the vent 3400 is located in a decoupling structure, e.g., a swivel.

5.4 RPT DEVICE 4000

A RPT device 4000 in accordance with one aspect of the presenttechnology comprises mechanical and pneumatic components 4100,electrical components 4200 and is programmed to execute one or morealgorithms. The RPT device (e.g. as shown in FIG. 4A) has an externalhousing 4010, for example formed in two parts, an upper portion 4012 anda lower portion 4014. Furthermore the external housing 4010 may includeone or more panel(s) 4015. The RPT device 4000 may comprise a chassis4016 that supports one or more internal components of the RPT device4000. In one form a pneumatic block 4020 is supported by, or formed aspart of the chassis 4016. The RPT device 4000 may include a handle 4018.

The pneumatic path of the RPT device 4000 (e.g. as shown in FIG. 4B) maycomprise an inlet air filter 4112, an inlet muffler 4122, a pressuredevice 4140 capable of supplying air at positive pressure (e.g., ablower 4142), and an outlet muffler 4124. One or more transducers 4270,such as pressure transducers 4272 and flow transducers 4274, may beincluded in, or coupled with, the pneumatic path.

The pneumatic block 4020 may comprise a portion of the pneumatic paththat is located within the RPT device 4000.

The RPT device 4000 may comprise electrical components 4200 such as anelectrical power supply 4210, one or more input devices 4220, a centralcontroller 4230, a therapy device controller 4240, a pressure device4140, one or more protection circuits 4250, memory 4260, transducers4270 (for example one or more of a flow transducer 41274, a pressuretransducer 4272 and a speed sensor 4276), data communication interface4280 and one or more output devices 4290 (for example a display 4294 anddisplay driver 4292). Electrical components 4200 may be mounted on asingle Printed Circuit Board Assembly (PCBA) 4202. In an alternativeform, the RPT device 4000 may include more than one PCBA 4202.

The central controller 4230 of the RPT device 4000 may be programmed toexecute one or more algorithm modules, such as a pre-processing module,a therapy engine module, a pressure control module, and a faultcondition module.

5.4.1 RPT Device Mechanical & Pneumatic Components 4100

5.4.1.1 Air Filter(s) 4110

An RPT device in accordance with one form of the present technology mayinclude an air filter 4110, or a plurality of air filters 4110.

For example, the air filter 4110 may be located at the beginning of thepneumatic path upstream of a blower 4142 as an inlet air filter 4112, orat the outlet of the RPT device 4000 as an outlet air filter 4114. SeeFIG. 4B.

5.4.1.2 Muffler(s) 4120

In one form of the present technology, an inlet muffler 4122 is locatedin the pneumatic path, such as upstream of a pressure device 4140 ordownstream of the pressure device 4140. See FIG. 4B.

5.4.1.3 Pressure Device 4140

In a form of the present technology, a pressure device 4140 forproducing a flow of air at positive pressure is a controllable blower4142. For example the blower may include a brushless DC motor 4144 withone or more impellers housed in a volute. The blower may be capable ofdelivering a supply of air, for example about 120 litres/minute, at apositive pressure in a range from about 4 cmH₂O to about 20 cmH₂O, or inother forms up to about 30 cmH₂O. The blower may include a blower asdescribed in any one of the following patents or patent applications thecontents of which are incorporated herein in their entirety: U.S. Pat.Nos. 7,866,944; 8,638,014; 8,636,479; and PCT patent applicationpublication number WO 2013/020167.

5.4.1.4 Anti-Spill Back Valve 4160

In one form of the present technology, an anti-spill back valve islocated between the humidifier 5000 and the pneumatic block 4020. Theanti-spill back valve is constructed and arranged to reduce the riskthat water will flow upstream from the humidifier 5000, for example tothe motor 4144.

5.4.1.5 Air Circuit 4170

An air circuit 4170 in accordance with an aspect of the presenttechnology is constructed and arranged to allow a flow of air betweenthe pneumatic block 4020 and the patient interface 3000. In some forms,the air circuit 4170 may comprise a heating element configured to heatthe flow of air travelling through the air circuit 4170. One example ofan air circuit 4170 comprising a heating element is disclosed in U.S.Pat. No. 8,733,349, the entire contents of which is incorporateherewithin by reference.

In one form, the air circuit 4170 may comprise a plurality of zones,each comprising a heating element 4171 that may be controlledindependently of each other.

5.4.1.6 Oxygen Delivery

In one form of the present technology, supplemental oxygen 4180 isdelivered to one or more points in the pneumatic path, such as upstreamof the pneumatic block 4020, to the air circuit 4170 or to the patientinterface 3000.

5.4.2 RPT Device Electrical Components 4200

5.4.2.1 Power Supply 4210

In one form of the present technology power supply 4210 is internal ofthe external housing 4010 of the RPT device 4000. In another form of thepresent technology, power supply 4210 is external of the externalhousing 4010 of the RPT device 4000.

In one form of the present technology power supply 4210 provideselectrical power to the RPT device 4000 only. In another form of thepresent technology, power supply 4210 provides electrical power to bothRPT device 4000 and humidifier 5000.

5.4.2.2 Input Devices 4220

In one form of the present technology, an RPT device 4000 includes oneor more input devices 4220 in the form of buttons, switches or dials toallow a person to interact with the device. The buttons, switches ordials may be physical devices, or software devices accessible via atouch screen. The buttons, switches or dials may, in one form, bephysically connected to the external housing 4010, or may, in anotherform, be in wireless communication with a receiver that is in electricalconnection to the central controller 4230.

In one form the input device 4220 may be constructed and arranged toallow a person to select a value and/or a menu option.

5.4.2.3 Central Controller 4230

In one form of the present technology, the central controller 4230 is adedicated electronic circuit configured to receive input signal(s) fromthe input device 4220, and to provide output signal(s) to the outputdevice 4290 and/or the therapy device controller 4240.

In one form, the central controller 4230 is an application-specificintegrated circuit. The central controller 4230 may comprise discreteelectronic components.

In another form of the present technology, the central controller 4230is a processor suitable to control an RPT device 4000 such as an x86INTEL processor.

A processor suitable to control an RPT device 4000 in accordance withanother form of the present technology includes a processor based on ARMCortex-M processor from ARM Holdings. For example, an S™32 seriesmicrocontroller from ST MICROELECTRONICS may be used.

Another processor suitable to control an RPT device 4000 in accordancewith a further alternative form of the present technology includes amember selected from the family ARMS-based 32-bit RISC CPUs. Forexample, an STR9 series microcontroller from ST MICROELECTRONICS may beused.

In certain alternative forms of the present technology, a 16-bit RISCCPU may be used as the processor for the RPT device 4000. For example, aprocessor from the MSP430 family of microcontrollers, manufactured byTEXAS INSTRUMENTS, may be used.

The central controller 4230 may be configured to receive inputsignal(s), such as input signals from one or more transducers 4270, oneor more humidifier transducers and one or more input devices 4220.

The central controller 4230 may be configured to provide outputsignal(s) such as to one or more of an output device 4290, a therapydevice controller 4240, a data communication interface 4280 andhumidifier controller 5550.

In some forms of the present technology, the central controller 4230, ormultiple such central controllers, may be configured to implement theone or more methodologies described herein such as the one or morealgorithms expressed as computer programs stored in a non-transitorycomputer readable storage medium, such as memory 4260. In some cases, aspreviously discussed, such processor(s) may be integrated with an RPTdevice 4000. However, in some forms of the present technology theprocessor(s) may be implemented discretely from the pressure generationcomponents of the RPT device 4000, such as for purpose of performing anyof the methodologies described herein without directly controllingdelivery of a respiratory treatment. For example, such a processor mayperform any of the methodologies described herein for purposes ofdetermining control settings for an RPT device by analysis of storeddata such as from any of the sensors described herein.

5.4.2.4 Clock 4232

The RPT device 4000 may include a clock 4232 that is connected to acentral controller 4230. The clock is configured to at least one ofmonitor, count or record time.

5.4.2.5 Therapy Device Controller 4240

In one form of the present technology, therapy device controller 4240 isa pressure control module that forms part of the algorithms executed bythe central controller 4230.

In one form of the present technology, therapy device controller 4240 isa dedicated motor control integrated circuit. For example, in one form aMC33035 brushless DC motor controller, manufactured by ONSEMI is used.

5.4.2.6 Protection Circuits 4250

An RPT device 4000 in accordance with the present technology comprisesone or more protection circuits 4250.

One form of protection circuit 4250 in accordance with the presenttechnology is an electrical protection circuit.

One form of protection circuit 4250 in accordance with the presenttechnology is a temperature and/or pressure safety circuit.

5.4.2.7 Memory 4260

In accordance with one form of the present technology the RPT device4000 includes memory 4260, e.g., non-volatile memory. In some forms,memory 4260 may include battery powered static RAM. In some forms,memory 4260 may include volatile RAM.

The memory 4260 may be located on PCBA 4202. Memory 4260 may be in theform of EEPROM, or NAND flash.

Additionally or alternatively, the RPT device 4000 may include removableform of memory 4260, for example a memory card made in accordance withthe Secure Digital (SD) standard.

In one form of the present technology, the memory 4260 acts as anon-transitory computer readable storage medium on which is storedcomputer program instructions expressing the one or more methodologiesdescribed herein, such as the one or more algorithms

5.4.2.8 Transducers 4270

Transducers may be internal or external of the RPT device 4000. Externaltransducers may be located for example on or form part of the aircircuit 4170 humidifier 5000 and/or the patient interface 3000. Externaltransducers 4270 may be in the form of non-contact sensors such as aDoppler radar movement sensor that transmit or transfer data to the RPTdevice.

In one form of the present technology, one or more transducers 4270 maybe constructed and arranged to measure properties of the air, such as atone or more points in the pneumatic path or of ambient air. In anotherform, one or more transducers 4270 may be configured to measureproperties of the RPT device 4000 such as motor speed and/or motorcurrent.

5.4.2.8.1 Flow Transducer 4274

A flow transducer 4274 in accordance with the present technology may bebased on a differential pressure transducer, for example, an SDP600Series differential pressure transducer from SENSIRION. The differentialpressure transducer is in fluid communication with the pneumaticcircuit, with one of each of the pressure transducers connected torespective first and second points in a flow restricting element.

In use, a signal representing total flow Qt from the flow transducer4274 is received by the central controller 4230.

5.4.2.8.2 Pressure Transducer 4272

A pressure transducer 4272 in accordance with the present technology islocated in fluid communication with the pneumatic circuit. An example ofa suitable pressure transducer is a sensor from the HONEYWELL ASDXseries. An alternative suitable pressure transducer is a sensor from theNPA Series from GENERAL ELECTRIC.

In use, a signal from the pressure transducer 4272 is received by thecentral controller 4230. In one form, the signal from the pressuretransducer 4272 may be filtered prior to being received by the centralcontroller 4230.

5.4.2.8.3 Motor Speed Sensor 4276

In one form of the present technology a motor speed signal is generated.A motor speed signal may be provided by therapy device controller 4240.Motor speed may, for example, be generated by a speed sensor, such as aHall effect sensor.

5.4.2.9 Data Communication Interface 4280

In one form of the present technology, a data communication interface4280 may be provided, and may be connected to central controller 4230.Data communication interface 4280 may be connectable to remote externalcommunication network 4282. Data communication interface 4280 may beconnectable to local external communication network 4284. Preferablyremote external communication network 4282 is connectable to remoteexternal device 4286. Preferably local external communication network4284 may be connectable to local external device 4288.

In one form, data communication interface 4280 may be part of centralcontroller 4230. In another form, data communication interface 4280 maybe an integrated circuit that is separate from central controller 4230.

In one form, remote external communication network 4282 may be theInternet. The data communication interface 4280 may use wiredcommunication (e.g. via Ethernet, or optical fibre) or a wirelessprotocol to connect to the Internet.

In one form, local external communication network 4284 utilises one ormore communication standards, such as Bluetooth, or a consumer infraredprotocol.

In one form, remote external device 4286 may be one or more computers,for example, a cluster of networked computers. In one form, remoteexternal device 4286 may be virtual computers, rather than physicalcomputers. In either case, such remote external device 4286 may beaccessible to an appropriately authorised person such as a clinician.

The local external device 4288 may be a personal computer, mobile phone,tablet or remote control.

5.4.2.10 Output Devices 4290 Including Optional Display, Alarms

An output device 4290 in accordance with the present technology may takethe form of one or more of a visual, audio and haptic unit. A visualdisplay may be a Liquid Crystal Display (LCD) or Light Emitting Diode(LED) display.

5.4.2.10.1 Display Driver 4292

A display driver 4292 receives as an input the characters, symbols, orimages intended for display on the display 4294, and converts them tocommands that cause the display 4294 to display those characters,symbols, or images.

5.4.2.10.2 Display 4294

A display 4294 is configured to visually display characters, symbols, orimages in response to commands received from the display driver 4292.For example, the display 4294 may be an eight-segment display, in whichcase the display driver 4292 converts each character or symbol, such asthe figure “0”, to eight logical signals indicating whether the eightrespective segments are to be activated to display a particularcharacter or symbol.

5.5 HUMIDIFIER 5000

5.5.1 Humidifier Overview

In one form of the present technology as shown in FIG. 7 , there isprovided a humidifier 5000 for increasing a moisture content, orabsolute humidity, of a flow of air in relation to the ambient air (airsurrounding the patient), before the flow of air is delivered to theentrance of the patient's airways. The humidifier 5000 is configured tobe coupled directly or indirectly, via an air circuit 4170, to an RPTdevice 4000 for receiving the flow of air. The humidifier 5000 may beplaced upstream or downstream of the RPT device 4000. In one example,the humidifier 5000 may deliver a flow of humidified air atapproximately 70%-90% relative humidity such as 80% relative humidityand approximately 25° C.-30° C. such as 27° C.

The humidifier 5000 may comprise an air inlet 5002 to receive a flow ofair, and an air outlet 5004 to deliver the flow of air with addedhumidity.

5.5.2 Humidifier Components

5.5.2.1 Reservoir 5110

According to one aspect of the present technology, the humidifier 5000may comprise (or be coupled to) a reservoir 5110 as shown in FIG. 8 .The reservoir 5110 may be configured to hold a predetermined, maximumvolume of water (or other suitable liquids, such as medications,scenting agents or a mixture containing such additives), which may beused to increase absolute humidity of the flow of air.

In one form, the reservoir 5110 may be configured to hold severalhundred millilitres of water, for use during at least the length of thepatient's sleep in a day. However, in other forms, other sizes such as asmaller reservoir for a portable, travel-friendly system or a largerreservoir for a hospital system may be also suitable. Yet further, areservoir 5110 may be replaced by, or connected to, a water supply.

According to some arrangements, the reservoir 5110 may comprise, or becoupled to, a water volume detector 5112 by which the amount of water inthe reservoir 5110 may be determined. The water volume detector 5112 maydetermine the volume of water based on one or more of a presence,weight, optical property, ultrasonic property or a head (height) of thewater of the reservoir 5110. Any of the mechanisms or methods such asthose described in the PCT Patent Application Number PCT/AU2014/050286may also be suitable for use with the present technology, the entirecontents of which is incorporated herewithin by cross-reference.

In some forms, the reservoir 5110 may be configured to heat the waterprior to the water entering the humidification chamber 5200, for exampleby comprising, or being coupled to, a reservoir heating element 5221 asshown in FIG. 8 .

In one form, the reservoir 5110 may comprise a plurality of liquidchambers, for example each containing a different fluid. In one example,a first chamber may comprise a volume of water while a second chambermay comprise medication (e.g. dissolved in liquid), or scenting agent(e.g. tea tree oils). The liquids from the plurality of liquid chambersmay be mixed prior to or during delivery to the humidifier or within thehumidifier 5000. Alternatively the humidifier may deliver one of theliquids from the plurality of liquid chambers at any one time.

5.5.2.2 Water Delivery Mechanism 5150

According to one aspect of the present technology, the humidifier 5000may comprise a water delivery mechanism 5150 configured to deliver aflow of water from the reservoir 5110 to a humidification chamber 5200(see FIG. 8 ). The water delivery mechanism 5150 may comprise a waterpump 5152 and a water delivery conduit 5154, and may be in fluidcommunication with a water feed inlet 5206 to deliver the flow of waterto the humidification chamber 5200. The water delivery mechanism 5150may additionally or alternatively comprise one or more of hydraulicchannels, capillary channels or holes. The water delivery mechanism 5150in some forms may further comprise a valve (e.g. water check valve 5158)for controlling delivery of water from the reservoir 5110 to thehumidification chamber 5200 but allowing and preventing delivery ofwater through to the water feed inlet 5206. For example, the valve maybe configured to controllably allow a flow of water to travel from thereservoir 5110 to the humidification chamber 5200, such as only when thehumidifier 5000 is in operation.

The humidification chamber 5200 may comprise a water retention featuresuch as a humidifier wick 5230, which receives the flow of water fromthe water delivery mechanism 5150. In some forms, the humidifier 5000may comprise a plurality of water delivery mechanisms 5150 and/or aplurality of water feed inlets 5206 in order to better control adistribution of water in the humidifier wick 5230 (e.g. more uniformly).In this disclosure, a water flow rate will be taken to mean a rate offlow of water from the reservoir 5110 to a humidification chamber 5200unless explicitly stated otherwise.

The water flow rate(s) that the humidifier 5000 is configured to providemay vary according to factors such as the configuration of thehumidifier 5000 and a range of expected operating conditions such asambient conditions (e.g. ambient temperature/humidity), humidifieroperating parameters (e.g. maximum heat output of the heating element5220, maximum water capacity of the humidifier wick 5230) and/or therapyconditions (e.g. therapy pressure, air flow rate, patientcomfort/preference). For example, a change in therapy pressure only maycause a change in the water flow rate, such as due to a response by thehumidifier controller 5550, or due to a property of the water deliverymechanism 5150.

In one form, the range of water flow rates able to be provided by thehumidifier 5000 may be between 0 ml/min and 2 ml/min, for examplebetween 0 ml/min and 1 ml/min, or between 0 ml/min and 0.5 ml/min. Inone form, the humidifier 5000 may be configured to provide one of anumber of discrete water flow rates, for example 0.0 ml/min, 0.2 ml/min,0.4 ml/min, 0.6 ml/min or 0.8 ml/min where the limits of water flowrates able to be provided are 0.0 ml/min and 0.8 ml/min. In other forms,the humidifier 5000 may be configured to provide any water flow ratebetween an upper limit and a lower limit by providing an analoguecontrol of the flow rate. The upper limit and lower limit of water flowrates may vary according to aspects of a humidifier, such as one or moreof: maximum humidity output, maximum flow rate of air through thehumidifier, a size of the humidifier and properties of the wick (e.g.exposed surface area and/or water capacity). In cases where at least oneliquid other than (or additional to) water is used, the flow rates foreach liquid may vary accordingly. The flow rate at a particular timeduring operation of the humidifier 5000 may also depend on the set ofoperating conditions at the particular time. For example, a typicalvalue with an air flow rate of 35 l/min and desired added humidity of 15mg/l requires a water flow of 0.5 ml/min

It is noted that air flow rates in respiratory therapy may vary over ashort term, for example, due to a breath cycle of a patient. However, insome examples, such as determining an appropriate water flow rate basedon an air flow rate, a humidifier algorithm may utilise an air flow ratewhere effects of such variation is removed, or reduced. Thus the airflow rate may be low-pass filtered, or be based on a continuous average,wherein the time constant (e.g. in filtering, or an average time) wouldbe sufficiently long to reduce or remove the effects of in-breathvariations.

A pressure of the flow of air (also known as air pressure) in an RPTdevice and its pneumatic path downstream thereof may vary duringtherapy, for example between 4 and 30 cmH₂O. Thus, the water pump 5152may be configured to deliver a consistent water flow rate across variousair pressures in the humidifier 5000. The water flow rate provided bythe water pump 5152 may be independent from (i.e. not be affected by)the air pressure in the humidifier 5000. Such a water pump 5152 would beadvantageous in that the air pressure may be varied independently of theamount of humidification provided thereto for improved controllabilityof the therapy system.

In one form, the water pump 5152 may be a positive displacement typepump. In another form, many other types of pumps such as metered pumps,peristaltic pumps, gravity-fed pumps, or pumps utilising blower pressuremay be suitable to be used in the water delivery mechanism 5150. Anelevated reservoir (not shown) such as a drip bag may also be suitableand act as a type of gravity fed pump to deliver water.

In some forms, where a water flow rate through the water pump 5152 maybe affected by the air pressure, the flow rate through the water pump5152 may be compensated accordingly. For instance as shown in FIG. 8 ,the water delivery mechanism 5150 may additionally comprise one or moreof a metering mechanism 5156 to measure and/or a water check valve 5158to control the water flow rate through the water pump 5152.Alternatively, the humidifier controller 5550 may be used to compensatefor the effects of any changes to the air pressure, by controlling thewater pump 5152 according to the air pressure. A measure of the airpressure may be received by the humidifier controller 5550 as an inputto enable such control. In some forms, the humidifier controller 5550may be used to compensate for the effects of any changes to the air flowrate (e.g. due to a change in leak), by controlling the water flow ratethrough the water delivery mechanism 5150.

In another arrangement (not shown), a water pump 5152 may be configuredto pump water by utilising a pressure such as that generated by the RPTdevice 4000. The pressure may then be used to draw water from thereservoir 5110 into the humidification chamber 5200. The water flow ratein such an arrangement may be a function of the air flow rate, and thusthe humidifier 5000 in this arrangement may further comprise a controlvalve to regulate the water flow rate.

The humidifier 5000 may in some forms comprise a fault detectionmechanism to detect conditions such as blockages in the water deliverymechanism 5150 or a shortage of water in the reservoir 5110, as will bedescribed in further detail below. For example, a blockage in a positivedisplacement pump may cause its motor to stall, causing the pump tostop. Furthermore, the humidifier 5000 may be configured to detectaccumulation of precipitates and/or contamination, such as in thehumidifier wick 5230, as precipitants or contaminants may adverselyaffect performance of the humidifier 5000, such as the wick by reducingthe ability of the humidifier wick 5230 to absorb water.

5.5.2.3 Humidification Chamber 5200

According to one aspect, the humidifier 5000 may comprise ahumidification chamber 5200, in which moisture is added to the flow ofair, thus increasing the absolute humidity, prior to being delivered tothe patient 1000. In one form, a cross-section of which is shown in FIG.9A, the humidification chamber 5200 may comprise a humidifier wick 5230,a water feed inlet 5206 and a heating element 5220.

The humidification chamber 5200 may be in fluid communication with, andreceives water from, the reservoir 5110 through the water feed inlet5206. The water feed inlet 5206 may comprise an inner diameter ofbetween about 0.5 mm to 3 mm in some forms, such as 1 mm, 1.5 mm, 2 mmor 2.5 mm. The water feed inlet 5206 may be sufficiently large to reducea risk of obstruction of the water feed inlet 5206, for example due to abuild-up of contaminants.

In one form, the humidification chamber 5200 may comprise an outerhousing 5202 configured to provide thermal insulation to the outside, aswell as to protect an interior of the humidification chamber 5200, suchas any components therein. The outer housing 5202 may comprise aplurality of portions such as an inlet portion 5202 a, heater coverportion 5202 b and outlet portion 5202 c that are coupled together. Theinlet portion 5202 a may comprise the air inlet 5002 and the outletportion 5202 c may comprise the air outlet 5004 as shown in FIG. 9A. Thewater feed inlet 5206 is shown located in the inlet portion 5202 a, butmay be located in any one of the portions 5202 a, 5202 b, 5202 c. Ifmultiple water feed inlets 5206 are present, the additional water feedinlets 5206 be located in one or more of the portions 5202 a, 5202 b,5202 c of the outer housing 5202. The heater cover portion 5202 b may beconfigured to locate and retain the heating element 5220. In somearrangements the heating element 5220 may be retained between an innerhousing 5204 and the heater cover portion 5202 b of the outer housing5202 as shown in FIG. 9A. The heating element 5220 may be bonded to theinner housing 5204 in some forms for improved heat conductivity betweenthe heating element 5220 and the humidification chamber 5200. The innerhousing 5204 is configured to isolate the heating element 5220 fromexposure to moisture, yet allow heat transfer to occur from the heatingelement 5220 to the humidifier wick 5230.

FIG. 9B shows a humidifier 5000 in another form according to the presenttechnology. In this form, the heater cover portion 5202 b of the outerhousing 5202 is set away from the heating element 5220 so as to providean air gap, for example for thermal insulation. The heater cover portion5202 b may also enclose the water feed inlet 5206 for protection asshown in FIG. 9B.

Suitable materials for the inner housing 5204 may include thermallyconductive materials, such as aluminium or its alloys, or thermallyconductive polymeric/thermoplastic materials such asPolycarbonate/Acrylonitrile Butadiene Styrene (PC/ABS), Polyamide (e.g.Nylon) or Polyphenylene Sulfide (PPS) that may comprise glass or carbonfill for improved thermal conductivity. The inner housing 5204 may be arigid material suitable to provide rigidity to the humidifier 5000,although in some forms, a flexible structure may be used where othercomponents of the humidifier provide sufficient structural rigidity.Suitable materials for the outer housing 5202 may include polymericmaterials such as PC/ABS, and the outer housing 5202 may includeelastomeric portions such as thermoplastic elastomer (TPE). The outerhousing 5202 may comprise a diameter of between about 10 mm and 50 mm,and be about 1-3 mm thick. The thickness of the inner housing 5204 maybe about 1-3 mm, and may vary according to the material used, forexample in order to achieve sufficient heat conductivity. It is to beunderstood that such dimensions and arrangements are exemplary and arenot intended to be limiting. It is to be understood that the innerhousing 5204 and/or the outer housing 5202 may have a different shape tothose shown and/or be formed of a different number of portions, such asone, two, four, five or more portions.

According to one aspect, the water feed inlet 5206 may be in fluidcommunication with the water delivery mechanism 5150 to deliver water tothe humidifier wick 5230 as shown in FIG. 8 . In some cases, thehumidifier 5000 may comprise a water filter 5214 configured to reduceingress of foreign matter into the humidification chamber 5200 and/orthe humidifier wick 5230 through the flow of water. The water filter5214 may be located at or near an outlet of the reservoir 5110 (as shownin FIG. 8 ) or upstream (prior to) the water feed inlet 5206. The waterfilter 5214, or parts thereof, may be configured to be replaceable orcleanable. In some forms (e.g. where quality of the water in thereservoir 5110 is low and/or where hardness of the water in thereservoir 5110 is high), the water filter 5214 may comprise a deioniser(not shown).

In some arrangements (not shown), the water feed inlet 5206 may belocated closer to the air outlet 5004 than the air inlet 5002. Such anarrangement may encourage at least some portion of the flow of water inthe humidifier wick 5230 to travel in an opposing direction to thedirection of the air flow in the humidification chamber 5200. Thus, thetemperature and humidification gradient within the water in thehumidifier wick 5230, as well as within the air flow may be optimised tooptimise the differential temperature and humidification therebetween inorder to improve humidification performance.

According to another aspect, the humidification chamber 5200 may furthercomprise an air flow baffle 5208 (as shown in FIG. 9A, 9B and FIG. 10 )configured to promote turbulence in the flow and/or increase theevaporative surface area, such as by extending a length and/or aresidence time during which the flow of air is in the humidificationchamber 5200, for example to improve humidification performance. In oneform, the air flow baffle 5208 may force the flow of air to travel in atortuous path, such as a helical path as shown in FIG. 10 to lengthen apath for the air travelling in the humidification chamber. Thus, the airflow baffle 5208 may comprise one or more baffle elements, each of whichmay be one or more of helical, inclined, curved, or otherwise arrangedto increase turbulence and/or to lengthen an air flow path in thehumidification chamber 5200. For example, the air flow baffle 5208 mayincrease the length of the path for the air flow through thehumidification chamber 5200 by between approximately 20% andapproximately 1000%, in comparison to a linear length of thehumidification chamber 5200. In other words, without the baffle 5208 theflow of air through the humidification chamber 5200 would be able topass directly or linearly from the air inlet 5002 to the air outlet5004. However, the addition of the baffle 5208 would serve to increasethe distance or lengthen the path that the flow of air must travel totraverse the humidification chamber 5200 from the air inlet 5002 to theair outlet 5004. For example, the length of the path may be lengthenedby between approximately 50% and approximately 750%, such as betweenapproximately 100% and approximately 300%, such as approximately 200%.It will be understood that in various examples of the presenttechnology, the amount of lengthening by the air flow baffle 5208 mayvary depending on particular arrangements and/or requirements of thehumidifier 5000.

Inclusion of the air flow baffle 5208 in a humidification chamber 5200may help reduce a size, such as a length, of the humidification chamber5200, in comparison to a length of the path for the air flow in thehumidification chamber 5200 used without such an air flow baffle 5208.Alternatively, or additionally, the humidification chamber 5200 mayfurther comprise one or more air flow trip elements 5209 along anevaporation surface, the air flow trip elements 5209 being configured toimprove humidification performance by increasing a turbulence of the airflow. An air flow trip element 5209 (also referred to herein as a ‘tripelement’) may comprise an obstruction to air flow, for example, a raisedstep, or surface. A trip element 5209 may increase an amount ofturbulence (e.g. as measured by a Reynolds number), whereby a thicknessof a boundary layer is reduced, encouraging moisture transfer from thehumidifier wick 5230 to the air flow. In some forms, the trip element5209 may present the obstruction to air flow in a directionsubstantially perpendicular to the direction of the air flow. Oneexample of a trip element 5209 is an annular prism structure located onan inner periphery of the inner housing 5204 as shown in FIG. 33 .

In some forms of the present technology the air flow baffle 5208 maycomprise a membrane. The air flow baffle 5208 may also further compriseacoustic elements for noise reduction, such as a tuned chamber (orresonator) configurations, or a number of narrow flow paths configuredto encourage development of laminar flow and reduce noise. In one form,the flow paths formed by the air flow baffle 5208 may be configured toprovide a high inertance to assist in reducing radiated noise. In somearrangements, the air flow baffle 5208 may comprise variable dampingproperties for reducing noise and/or vibrations.

In some arrangements, the humidification chamber 5200 may comprise abypass port for sensing one or more properties of the flow of air as itpasses through the humidification chamber 5200.

Additionally, or alternatively, the humidification chamber 5200 may beconfigured to only add humidity to the flow of air for an inhalationphase of a patient's breath. In one form, the humidifier 5000 maycomprise a bypass path which may be used to divert the air flow awayfrom the humidification chamber 5200 for at least a part of a breathcycle, for example using a valve. This may allow for delivery of an airflow to the patient interface 3000 without humidification during someparts of a breath cycle, such as during exhalation.

5.5.2.3.1 Heating Element 5220

The amount of moisture, or absolute humidity, that a flow of air is ableto retain in vapour form varies according to a temperature of the flowof air.

In some cases, the flow of air received by the humidifier 5000 may betoo cold to retain adequate absolute humidity for delivery to theentrance to the airways of the patient 1000. Furthermore, delivery ofcold air may cause discomfort to the patient 1000 as described above.Thus, a humidifier 5000 may comprise a heating element 5220 configuredto output heat, for example to heat the flow of air. In one form, theheating element 5220 may be located in the humidification chamber 5200,such as between the inner housing 5204 and the outer housing 5202 asshown in FIG. 9A. Alternatively, or additionally, the reservoir 5110 maycomprise a reservoir heating element 5221 to heat water prior to itentering the humidification chamber 5200 as shown in FIG. 8 .

The heating element 5220 may heat the flow of air as it passes throughthe humidifier 5000, as well as to assist humidification in thehumidification chamber 5200 such as by heating the humidifier wick 5230.Accordingly, the heating element 5220 may be configured so that itprovides sufficient thermal energy for heating and vaporisation at thehighest requirements respectively, that is, where the ambient air iscold and dry.

The heating element 5220 may be configured in one of a number of wayswhilst meeting the above requirements. In one form, a heating element5220 may comprise an approximately 10 cm² surface area that generates amaximum thermal output of 40 Watts. In another form, a heating element5220 may comprise an approximately 40 cm² surface area with the samemaximum thermal output value of 40 Watts. It should be understood thatthe maximum thermal output value need not be limited to 40 Watts, andthe surface area of the heating element 5220 may be arranged accordingto aspects of the humidifier 5000, such as its maximum thermal output,size and/or shape. For example, the heating element 5220 may comprise asurface area sized between approximately 5 and 100 cm², such as betweenapproximately 10 and 60 cm², or between approximately 20 and 40 cm².Examples of relationships between a power output of a humidifier 5000are shown in FIG. 17 and FIG. 19 , and an example of a relationshipbetween added humidity and temperature of the heating element is shownin FIG. 18 . It should be understood that a size and/or heat output ofthe heating element 5220 may vary in particular examples of the presenttechnology. For example, a heating element 5220 may be larger in ahumidifier 5000 configured to deliver a higher humidification and/orheat than in a humidifier 5000 configured to deliver a lowerhumidification and/or heat. In some forms, a heating element 5220 for ahumidification chamber 5200 comprising a larger surface area would belarger than a heating element 5220 for a humidification chamber 5200comprising a smaller surface area.

According to one aspect of the present technology, the heating element5220 may be zoned. That is, the heating element 5220 may comprisemultiple sections, or zones, that may be controlled discretely and/orhave variable properties. In some cases, variable properties of thezones may include shape, heat output, insulation, proximity to thehumidifier wick 5230 or proximity to water feed inlet 5206. Yet further,each zone may be controlled independently of each other by thehumidifier controller 5550, and in some cases controlled relative toeach other. An example of a heating element 5220, which may allowrelative control of the zones, is shown in FIG. 11 . In this example,the heating element 5220 may comprise four zones 5220_1, 5220_2, 5220_3and 5220_4, wherein the heating output of each zones may be configuredto be varied between 0 to 100% of a total heat output of the heatingelement 5220, for example 0%, 10%, 20%, 30% and 40% of a total heatoutput of the heating element 5220. There may be a different number ofheating zones, such as two, three, five or more zones and properties ofthe zones such as their shape, size or maximum heat output may vary.Each zone may be contiguous with another, although they may be spacedapart in some forms. In some forms, each zone may have varying densityof electrically conductive circuits therein to achieve varying heatingoutputs in each zone.

One suitable form of a heating element 5220 may comprise a resistiveelectrical track on a circuit board. The circuit board may comprise asubstrate which could be used as a thermally conductive, electricallyresistive barrier between the resistive electrical track and thehumidifier wick 5230. In one form, the heating element 5220 may comprisea flexible circuit board. In another form, the heating element 5220 maycomprise a metallic thermally conductive substrate, which is separatedby a dielectric laminate layer from the heating track. Alternative formsof a heating element 5220 may also be suitable such as an inductiveheater, if the heating element 5220 is configured to be able to providea heat output to the humidifier wick 5230 and/or the humidificationchamber 5200.

A substrate of a heating element 5220 may comprise at least a part of ahumidifier wick 5230. Thus, the substrate may comprise an absorptivematerial such as one or more of: paper, felt, woven material, or anyabsorbent thin film. An electrical circuit may be disposed onto thesubstrate to provide the resistive electrical track, such as byprinting, by chemical bonding, by an adhesive, or by interweaving forexample. In one form, a conductive ink comprising an electricallyconductive material may be printed onto the absorptive substrate,whereby the conductive circuit may be formed onto a surface of theabsorptive substrate.

The conductive circuit may be connected to one or more sensors such asthose described elsewhere in the present document. Additionally, oralternatively, the conductive circuit may comprise a variable resistanceportion where the electrical resistance may vary according to aparameter. Examples of variable resistance portions may include apositive temperature coefficient portion, or a negative temperaturecoefficient portion. A variable resistance portion may be used as asensing element, for example to sense a temperature at or near thevariable-resistance portion according to a change in its resistance. Apositive temperature coefficient (PTC) portion may be disposed onto anabsorptive substrate by printing PTC carbon ink onto a paper substrate.

In some forms, electrically insulating materials may be disposed onto anabsorptive substrate to insulate any conductive portions disposedthereon. For example, an insulating layer comprising dielectric ink maybe printed to insulate a conductive circuit comprising conductive inksprinted onto a paper substrate.

In another form, the resistive electrical track of the heating element5220 may comprise a resistive wire. The resistive wire may wrap aroundan outer housing 5202 as shown in FIG. 20 , for example by forming aplurality of loops around the surface. In one example, each strand ofwire may be bonded to adjacent strand(s) of wire, such as by an adhesive(e.g. epoxy). In another example, each strand of wire may comprise aninsulating layer, which may be further configured to bond to adjacentstrand(s) of wire when heat is applied thereto. Thus the plurality ofloops of the resistive wire may be formed around the outer housing 5202,and heat may be applied to the heating element 5220 (e.g. externally, orby applying a current through the heating element 5220) to bond thestrands together.

As described above, the heating element 5220 may take one of a number ofpossible forms in shape and/or construction. Thus, it should beunderstood that although the heating element 5220 is shown (e.g. in FIG.9A and FIG. 11 ) to be a cylindrical shape, it need not be limited tosuch a shape. For example, the heating element 5220 may be constructedas a flat, rectangular sheet, as an extruded arc shape, as a rectangularprism, or a plurality of parallel sheets, among others.

The heating element 5220 may be disposable in some cases. For instance,the entire humidification chamber 5200 may be disposable wherein theheating element 5220 is formed integrally within the humidificationchamber 5200 as a part of a disposable component. Alternatively, theheating element 5220 may be configured to be disposable and easilyreplaced by removal from the humidification chamber 5200, for example byinserting, such as sliding, into the humidification chamber 5200 forinstallation.

5.5.2.3.2 Humidifier Wick 5230

In one aspect of the present technology, the humidifier 5000 maycomprise a water retention feature such as a humidifier wick 5230. Thewater retention feature (e g humidifier wick 5230) may be configured toretain a volume of water, which may be received from the reservoir 5110for evaporation to humidify the flow of air before it is delivered tothe patient 1000. The water retention feature may be shaped so that itmay substantially define a part of an air path from the RPT device 4000to the patient interface 3000. The water retention feature may define,e.g., wholly define, a part of the air path by forming a substantiallyenclosed path, such as a cylindrically shaped path. In other words, thewater retention feature may surround or substantially surround at leasta portion of a flow path for the flow of air through the humidifier5000.

For example, the water retention feature, e.g., the humidifier wick 5230may have a profiled shape to enclose or substantially enclose at least aportion of the flow path of the air in an axial direction. In theexamples depicted in FIGS. 7-10, 12-16 , and 31-34, the humidifier wick5230 may be understood to have a profiled shaped in the form of asubstantially circular cross-section. However, it should also beunderstood that the humidifier wick 5230 may have a profiled shape inthe form of a U-shaped cross-section, a V-shaped cross-section, an oval,elliptical, or ellipsoidal cross-section, a polygonal cross-section(i.e., the cross-section may have any number of sides so long as theinterior of the humidifier wick 5230 is enclosed), or a paraboliccross-section. It should also be understood that the humidifier wick5230 may have a profiled shape that completely encloses the interior ofthe humidifier wick 5230 and at least a portion of the flow path of airtherein, e.g., as in a circular cross-section, an oval, elliptical, orellipsoidal cross-section, or a polygonal cross-section. Alternatively,the humidifier wick 5230 may have a profiled shape that does notcompletely enclose the interior of the humidifier wick 5230 and at leasta portion of the flow path of air therein, e.g., as in a U-shapedcross-section or a V-shaped cross-section.

In an example of the present technology, the humidifier wick 5230 mayhave a profiled shape that defines a surface which directly contacts theflow of air therethrough and that surface has a profiled shape in thatthe surface is not substantially planar. In other words, the surface maybe understood to be three-dimensional in nature and not two-dimensional.

In order to achieve a target level of humidification output whilstmaintaining a small size for the humidifier 5000, it may be beneficialfor the water retention feature to wholly define a part of the air pathto maximise a contact area with the air flow. Such an arrangement mayallow the water retention feature to be disposed entirely around aperiphery of the air path, such that for a given length of the waterretention feature the area of contact between the air path and the waterretention feature is maximised. For example, the humidifier wick 5230shown in FIG. 10 is shaped as a hollow cylinder to fit within acylindrically shaped humidification chamber 5200, and define acylindrically shaped, enclosed air path therethrough. It will beunderstood that of course, other shapes may also be suitable.

A maximum volume of water able to be retained by the humidifier wick5230, or a water capacity of the humidifier wick 5230, may bepredetermined. In one aspect, the water capacity of the humidifier wick5230 may be small enough to ensure a short response time of thehumidifier 5000. That is, the humidifier 5000 may be able to effect achange to its output (e.g. humidity and/or temperature output) in arelatively short period of time. It would be understood by those skilledin the art that a response time of a humidifier 5000 is a function ofthe volume of water that is heated. Thus, a humidifier 5000 according tothe present technology may comprise a relatively short response time. Insome forms of the present technology, a humidifier 5000 may comprise asufficiently short response time such that a heat and/or a humidityoutput of the humidifier 5000 may be varied within approximately aminute, such as within 45 seconds, within 30 seconds, or within 15seconds.

According to another aspect, the water capacity of the humidifier wick5230 is sufficiently large to allow adequate humidification at thehighest flow rates and driest ambient conditions. In one form, thehumidifier wick 5230 may thus comprise an adequately large surface areafor the water contained therein to come in contact with the air flowthrough the humidifier 5000. The water capacity of the humidifier wick5230 may be approximately 10 grams (g), however other values may also beappropriate such as approximately 2 g, 6 g, 15 g, 20 g, 30 g, or anyother values therebetween. In other forms, a larger or a smaller watercapacity of the humidifier wick 5230 may be suitable depending upon thesize and application of the humidifier.

A condition wherein the water capacity of the humidifier wick 5230 ismet by the water content in the humidifier wick 5230 may be referred toas ‘saturation’ or ‘flooding’ of the humidifier wick 5230. In somecases, the humidifier 5000 may be operated such that the humidifier wick5230 is not saturated during use. Disadvantages caused by saturation ofthe humidifier wick 5230 may include introduction of water droplets inthe humidifier 5000 and/or the air circuit 4170 due to transportation ofunabsorbed water from the humidifier wick 5230 (e.g. by entrainment intothe air flow). Detection of saturation of the humidifier wick 5230 maybe thus desirable, which will be described in further detail below. Insome cases, the air circuit 4170 may comprise a portion of thehumidifier wick 5230, or a secondary wick (or water trap), to ameliorateany potential problems related to such transportation, such as byabsorbing any transported water or condensation.

According to one aspect, the humidifier wick 5230 may be constructedwith non-homogenous geometry and/or construction (e.g. anisotropicallyor in zones). Thus, one or more properties of the humidifier wick 5230such as the water capacity, surface area exposed to air, or heatconductivity may be varied, such as for each area of the humidifier wick5230 or according to a direction. For instance, the humidifier wick 5230may be non-homogenous along the direction of air flow, or along adistance from the water feed inlet 5206, for example the thickness ofthe humidifier wick 5230 may vary, such as the humidifier wick 5230 maybecome thinner the further away from the water feed inlet 5206. In oneform, geometry of the humidifier wick 5230 may vary in one or more ofthe depth, number of layers, the density and/or material of thehumidifier wick 5230.

For example, the humidifier wick 5230 may comprise one or more layers,such as a first layer 5230 a and a second layer 5230 b as shown in FIG.12 . The one or more layers may vary in form and/or functions. In oneinstance, the first layer 5230 a may be a transport layer incommunication with the water feed inlet 5206, and the second layer 5230b may be an evaporation layer laid over the first layer 5230 a and incontact with the flow of air. In this construction, the first layer 5230a may be configured to optimise storage of water per volume and/or fasttransport of water, and the second layer 5230 b may be configured forimproved evaporation characteristics, for example, by increasing anexposed surface area per volume. In some forms, the humidifier wick 5230may be configured so that one or more layers may be replacedindependently of each other, wherein the one or more layers may or maynot be identical in form and/or function.

In one form, a humidifier wick 5230 may be anisotropically constructedso that a rate of wicking may be greater in a first direction than in asecond direction. Such a construction may allow a distribution of waterto be biased in a predetermined manner. For example, the humidifier wick5230 may be configured so that the rate of wicking in a directionperpendicular to the air flow may be greater than the rate of wicking ina direction parallel to the air flow. Such a configuration may beadvantageous in maximising a rate of humidification of the air flow, asmore of different portions of the air flow may come into contact withthe humidifier wick 5230. The humidifier wick 5230 may beanisotropically configured in one or more directions, such as at 30degrees, 60 degrees or 90 degrees to the direction of the flow of air.

In some forms, the humidifier wick 5230 may comprise a surfaceconfigured to increase a total surface area exposed to the flow of air.This may increase the area over which the water retained by thehumidifier wick 5230 is in contact with the air flow and improvehumidification efficiency. For instance, the humidifier wick 5230 maycomprise a corrugated inner surface as shown in FIG. 13 . Other suitablesurface types may include one or more of: dimpled, perforated, porous,woven, knitted, textured and sintered surfaces.

A humidifier wick 5230 according to the present technology may comprisea single continuous component, multiple components working as anassembly, or a discontinuous, discrete collection of wicking materialsand/or elements. In the present document all or any of the abovevariations will be referred to as a ‘humidifier wick’ 5230. A personskilled in the art would understand that the humidifier wick 5230 neednot be constructed as a single piece of wicking material.

A humidifier wick 5230 may be located towards an outer periphery of thehumidifier 5000, such as in the example shown in FIG. 9A, where thehumidifier wick 5230 is shown to at form at least a part of the outerboundary of the air flow path through the humidifier 5000. Additionally,or alternatively, a humidifier wick 5230 may be located towards a centreof the humidifier 5000, for example as shown in FIG. 32 , such that thehumidifier wick 5230 is located away from the outer boundaries of theair flow path through the humidifier 5000. In the configuration shown inFIG. 32 , the humidifier 5000 may further comprise one or more wickstruts 5231 to locate and/or secure the humidifier wick 5230 in itsintended location. In one form, the one or more wick struts 5231 may beconfigured to removably engage the inner housing 5204 as shown in FIG.32 to locate and/or secure the humidifier wick 5230 in relation to theinner housing 5204.

In some forms (e.g. where the humidifier wick 5230 is located toward acentre of the humidifier 5000), the water feed inlet 5206 may comprise aprojection extending from an inner surface of the humidifier 5000towards the humidifier wick 5230, as shown in FIG. 32 , in order todeliver liquid from the reservoir 5110. The water feed inlet 5206 mayadditionally comprise a lead-in 5207, as shown in FIG. 32 , in thedirection of insertion of the humidifier wick 5230 to allowself-alignment during insertion of the humidifier wick 5230 into thehumidifier 5000.

According to another aspect, the humidifier wick 5230 may be heated, forexample, by the heating element 5220. One advantage of heating thehumidifier wick 5230 may be that a rate of evaporation may becontrolled. In one form, the humidifier wick 5230 may be thermallycoupled to the heating element 5220, for example by contact as shown inFIG. 12 , which may advantageously reduce thermal impedance between thehumidifier wick 5230 and the heating element 5220.

A humidifier wick 5230 may in some cases be only partially heated by theheating element 5220, for example by the heating element 5220 being inpartial thermal contact with of the humidifier wick 5230. In one form,the humidifier wick 5230 may comprise unheated regions upstream and/ordownstream of a heating element 5220, as well as a heated region whichis in thermal contact with the heating element 5220. A heated region5230H of the humidifier wick 5230 may overlap the heating element 5220,and an upstream unheated region 5230U and a downstream unheated region5230D may extend upstream and downstream of the heated region 5230Hrespectively, where they may not overlap the heating element 5220. Theupstream unheated region 5230U and/or the downstream unheated region5230D may also substantially not overlap any conductive portions of thehumidifier 5000 which are in close thermal contact with the heatingelement 5220, such as the inner housing 5204, as shown in FIG. 34 .

An upstream unheated region 5230U may be configured so that waterdelivered by the water feed inlet 5206 would spread faster within theupstream unheated region 5230U prior to spreading into or through theheated region 5230H of the humidifier wick 5230. For example, theupstream unheated region 5230U may comprise a higher wicking rate thanthe heated region 5230H. In such an arrangement, water in the upstreamunheated region 5230U may be allowed to spread therein prior tooccurrence of evaporation in the heated region 5230H. Thus, thehumidifier wick 5230 may result with an improved spatial distribution ofwater therein, where the water boundary is substantially consistent in adirection perpendicular to the air flow direction, such as in a radialdirection of the humidifier 5000.

A humidifier wick 5230 may comprise a downstream unheated region 5230D(as shown in FIG. 34 ), which may be used to provide additional waterretention capacity to mitigate against risks of transportation ofunabsorbed water from the humidifier wick 5230, for example. Forexample, a downstream unheated region 5230D may allow the a heatedregion 5230H of the humidifier wick 5230 to be saturated with water atall times while mitigating a risk of overflowing by providing additionalcapacity. Additionally, a downstream unheated region 5230D may captureunevaporated moisture which may be entrained and/or transporteddownstream of the heated region 5230H, such as by the air flow.

In one form, suitable lengths of the upstream unheated region 5230U maybe between approximately 5% and approximately 20% of the length of theheated region 5230H, between approximately 8% and approximately 15%,between approximately 8% and approximately 12%, or approximately 10%.For a humidifier 5000 comprising a heated region 5230H with a length of50 mm, a suitable length of upstream unheated region 5230U may bebetween approximately 2.5 mm and approximately 10 mm, betweenapproximately 4 mm and approximately 7.5 mm, between approximately 4 mmand approximately 6 mm, or approximately 5 mm. In one form, suitablelengths of the downstream unheated region 5230D may be betweenapproximately 10% and approximately 50% of the length of the heatedregion 5230H, between approximately 20% and approximately 40%, betweenapproximately 25% and approximately 35%, or approximately 30%. For ahumidifier 5000 comprising a heated region 5230H with a length of 50 mm,a suitable length of downstream unheated region 5230D may be betweenapproximately 5 mm and approximately 25 mm, between approximately 10 mmand approximately 20 mm, between 12.5 mm and 17.5 mm, or approximately15 mm

Size of the upstream unheated region 5230U and/or the downstreamunheated region 5230D may be varied according to aspects of thehumidifier 5000, such as its size (e.g. length and/or diameter),humidification output, size of the humidifier wick 5230, water capacityof the humidifier wick 5230, water flow rate and/or number of water feedinlets 5206.

A performance of the humidifier wick 5230 may degrade over time and/orusage, and in some cases the humidifier wick 5230 may no longer besuitable for use. For instance, foreign matter, such as particulatesfrom the water, may collect or build up on the humidifier wick 5230 asit is evaporated. In some cases, collection of foreign matter may reducewater capacity and/or heat conductivity of the humidifier wick 5230. Insome cases, the humidifier wick 5230 may deteriorate over time, possiblyeven without any use of the humidifier 5000. Still further, the foreignmatter collected on the humidifier wick 5230 may be removed from thehumidifier wick 5230 and be entrained onto the flow of air, which may beundesirable.

Thus, in one aspect of the present technology, the humidifier wick 5230may be cleaned and/or replaced. Furthermore a condition of thehumidifier wick 5230 may be determined, such as its water capacityand/or its remaining usable life, and provide an indication or messagewhen the humidifier wick 5230 needs replacing or to an expected time toreplacement.

According to another aspect, a pattern of distribution of foreign matteron the humidifier wick 5230 may be determined and/or controlled. Forinstance, the humidification chamber 5200 may be configured to encouragecollection of foreign matter on the humidifier wick 5230 according to apredetermined pattern. Still further, the predetermined pattern offoreign matter build-up on the humidifier wick 5230 may be used as anindicator of a remaining life of the humidifier wick 5230. For example,the humidifier wick 5230 may be configured so that foreign matter maybegin to collect from one predetermined region of the humidifier wick5230, and for the collection to grow in a predetermined direction. Then,detection of a build-up of foreign matter, for example in apredetermined life-indicator region may be used to indicate that thehumidifier wick 5230 may be no longer suitable for use. Thus,determination of a remaining life of the humidifier wick 5230 may bemade while the humidifier wick 5230 remains in the humidifier 5000.

A cross-section of the humidifier 5000 (wick frame 5232 not shown)showing an example arrangement of a humidifier wick 5230 in use is shownin FIGS. 14A and 14B. In this example, the humidifier wick 5230 holds avolume of water, however the volume of water may be less than the watercapacity of the humidifier wick 5230. Accordingly, the humidifier wick5230 may be shown to comprise of two regions, a wet region 5230_W and adry region 5230_D, separated by a water boundary, is shown as 5230_WB.Typically, formation or collection of any foreign matter from water ontothe humidifier wick 5230 may predominantly occur at the boundary edge,as this is the point at which particulates are dried. Accordingly, oneof the aspects of the present technology relates to a control of thewater boundary 5230_WB, through construction of the humidifier wick 5230and/or foreign matter management algorithms, as described further below.

In one form, the humidifier wick 5230 may be configured to allowwashing, e.g. in a dishwasher, disinfection using another agent, and/orusing a microwave. Additionally, or alternatively, the humidifier wick5230 may comprise an antimicrobial or antibacterial agent such assilver. Yet further, the humidifier 5000 may comprise self-cleaningalgorithms (such as a bio-burden reduction algorithm) as will bedescribed further below.

According to one aspect, the humidifier wick 5230 may further compriseadded matter such as a medication to be introduced to the flow of air,or a life indicator. The life indicator may comprise a coloured portionwhich changes colour to indicate to the user or the patient 1000 thatthe humidifier wick 5230 should be replaced. The humidifier wick 5230may comprise a medication which may be released by vaporisation to theflow of air to be delivered to the patient 1000.

Suitable materials for the humidifier wick 5230 may include (but notlimited to): paper, bicomponent materials comprising hydrophilic fibres,and cellulose fibres. A humidifier wick 5230 may comprise one or more ofthe above listed materials in one or more arrangements (e.g. flat,corrugated, isotropic, anisotropic, layered etc.) to achieve propertiesof the humidifier wick 5230 described within the present document.

The humidifier wick 5230 may comprise, or be combined with, the heatingelement 5220 in some cases. As described elsewhere in the presentdocument, the humidifier wick 5230 may comprise a conductive portion(e.g. a carbon ink) which may form resistive tracks for heating, and anabsorptive portion (e.g. paper) for water retention and evaporationwhich also acts as the substrate for the conductive portion. In oneform, the heating element 5220 may be coupled (e.g. printed) onto one orboth sides of the humidifier wick 5230 so as to create an integratedcomponent. The integrated component may further comprise one or moreconnectors which may be coupled (e.g. printed) onto one or both sides ofthe humidifier wick 5230, for example for connection to the controller5550.

The humidifier wick 5230 may be constructed from a sheet in some forms.For example, the humidifier wick 5230 may comprise a paper sheet whichhas been formed into a tubular shape, such as to conform to a shape tothe humidifier chamber. The sheet may be bonded by adhesives, onesuitable example of which is a hot melt open adhesive web. However, itwill be readily understood that a number of known alternatives may bealso suitable.

The humidifier wick 5230 may comprise one or more humidifiertransducers. The humidifier transducers and humidifier algorithms whichmay receive inputs from the humidifier transducers are described infurther detail below.

In another aspect, the humidifier wick 5230 may be configured in a shapeto facilitate easy insertion and/or removal with respect to thehumidification chamber 5200. In one form, a portion of the humidifierwick 5230 such as a tab (not shown) may be configured to be accessiblefor removal while the humidifier wick 5230 is in its operating position.Yet further, the humidifier 5000 may be configured as shown in FIGS. 14Aand 14B such that a component (such as an outer housing component5202_c) may be removed to allow access to the humidifier wick 5230.Additionally, or alternatively, the humidifier wick 5230 may beconfigured in a frustro-conical shape complementarily to a similarlyshaped humidification chamber 5200, so that it would self-locate duringinsertion into its operating position.

5.5.2.3.3 Wick Frame 5232

In some forms of the present technology, the humidifier 5000 maycomprise a wick frame 5232, such as an example shown in FIG. 9A, FIG. 9Band FIG. 10 . The wick frame 5232 may be coupled to the humidifier wick5230 (e.g. chemically bonded and/or mechanically coupled), for instanceto locate and/or shape the humidifier wick 5230 (e.g. in a predeterminedlocation and/or shape), maintain the humidifier wick 5230 in closeproximity to the heating element 5220, and/or to prevent an increase inflow impedance which may occur due to a deformation of the humidifierwick 5230. The wick frame 5232 may promote, or maintain, thermal contactbetween the humidifier wick 5230 and the heating element 5220 byassisting in locating and/or shaping the humidifier wick 5230 asdesigned (e.g. by maintaining the humidifier wick 5230 in a cylindricalshape as shown in FIG. 10 ). In a form shown in FIG. 10 , the wick frame5232 may comprise a wick locator 5233 such as a shoulder as shown, toassist in location of the humidifier wick 5230 in relation to the wickframe 5232 in assembly.

The wick frame 5232 may be further configured to assist in removaland/or insertion of the humidifier wick 5230 with respect to thehumidifier 5000, for instance by providing a grip 5232_G to assist auser and/or the patient 1000 to locate and/or hold the wick frame 5232for insertion, removal and/or handling of the wick frame 5232. In oneform, the grip 5232_G may comprise a flat plate-like configuration toallow the patient/user to hold the wick frame 5232, although any numberof other shapes and/or configurations may be also suitable. The grip5232_G may extend past an open end of a surrounding component, such asan inner housing 5204, although in some forms, the grip 5232_G may beaccessible from an exterior of the humidifier 5000, such as to allowremoval of the wick frame 5232 and/or the humidifier wick 5230 from anexterior of the humidifier 5000 (e.g. without disassembly of any othercomponents of the humidifier 5000). Additionally, or alternatively, thewick frame 5232 may comprise a connector (not shown) to removably locateand/or secure the humidifier wick 5230 to the humidifier 5000, such asby a bayonet, a thread, a friction-fit surface or a pin. Those skilledin the art will recognise that a number of other connectors may be alsoused to secure and/or locate the humidifier wick 5230 to the humidifier5000, such as to the outer housing 5202.

The grip 5232_G may be marked (e.g. using colours and/or indicators) foridentification, and/or textured to assist the users to hold onto thegrip 5232_G. In some forms, where the humidifier wick 5230 isdisposable, the wick frame 5232 may be configured to be disposed withthe humidifier wick 5230, for example by being integrally formed withthe humidifier wick 5230. In other cases, the wick frame 5232 may beconfigured to accept and hold the humidifier wick 5230, for example, sothat the humidifier wick 5230 may be replaced while the wick frame 5232is removed from the humidifier 5000. Then the wick frame 5232 may accepta new humidifier wick 5230 and be inserted into the humidifier 5000. Insome forms, the wick frame 5232, the humidifier wick 5230 and theheating element 5220 may be non-removably coupled together andconfigured to be disposable as a unit.

According to another aspect, the wick frame 5232 may be configured to beprinted by a 3-D printer, for example by the patient 1000, or acaregiver, such as in a hospital or in a home environment.Alternatively, or additionally, the wick frame 5232 may be moulded asone component, or an assembly of a plurality of moulded components. Insome forms, the humidifier wick 5230 and the wick frame 5232 may be asingle component.

In one form, the wick frame 5232 may further comprise one or more airfilters upstream and/or downstream of the humidifier wick 5230. The airfilter may be placed upstream of the humidifier wick 5230 in order toreduce introduction and/or collection of foreign matter onto the wick5230. Alternatively, or additionally, the air filter may be placeddownstream of the humidifier wick 5230 in order to reduce incidence ofany foreign matter travelling from the humidifier wick 5230 to thepatient 1000.

According to another aspect, the wick frame 5232 may comprise the airflow baffle 5208 described above. Where the wick frame 5232 is combinedwith the air flow baffle 5208, the humidifier wick 5230 may form onesurface of the path of the flow of air. This configuration may beadvantageous in that the length of contact is increased between the flowof air and the humidifier wick 5230, which may improve humidification.

5.5.2.3.4 Humidifier Filter 5240

One or more humidifier filters 5240 may be used in some arrangements ofthe humidifier 5000. The humidifier filter 5240 may be used to reducethe amount of undesirable components from the flow of air, for exampleby preventing the particulates that may have originated from evaporatedwater from being introduced into the flow of air. A humidifier filter5240 may be placed anywhere in the humidifier 5000, such as at or nearthe air inlet 5002 (as shown in FIGS. 14A and 14B), the air outlet 5004(as shown in FIG. 16 ), or therebetween (not shown). It should also beunderstood that more than one humidifier filter 5240 may be included. Afilter (not shown) located downstream of the humidifier 5000, forexample in the air circuit 4170, may substantially perform a similarfunction as a humidifier filter 5240 by reducing the amount ofundesirable component from the flow of air.

5.5.2.3.5 Pre-Delivery Chamber 5115

According to another aspect of the present technology, the humidifier5000 may comprise a pre-delivery chamber 5115, an example of which isshown in FIG. 31 . The pre-delivery chamber 5115 may receive and retaina volume of water from the reservoir 5110 prior to beginning delivery ofwater from the pre-delivery chamber 5115 to the water retentionmechanism (e.g. humidifier wick 5230), in order to deliver water to thehumidifier wick 5230. The pre-delivery chamber 5115 may be fluidlyconnected to the humidifier wick 5230 at a plurality of locations inorder to evenly deliver water to the humidifier wick 5230.

In the example shown in FIG. 31 , the pre-delivery chamber 5115 isshaped as a toroid prism, and is configured to receive water from thewater feed inlet 5206 and deliver water to the humidifier wick 5230. Thepre-delivery chamber 5115 may be configured so that a predeterminedamount of water is required in the pre-delivery chamber 5115 prior toany communication of water can occur from the pre-delivery chamber 5115to the humidifier wick 5230. Thus, in the example shown in FIG. 31 , thehumidifier wick 5230 may be fluidly coupled to the pre-delivery chamber5115 by a coupling which may only allow water therethrough after apredetermined amount of water is introduced into the pre-deliverychamber 5115.

In one form, the pre-delivery chamber 5115 may comprise walls made fromwater impermeable material, which may be flexible, such as Gore-tex™fabric or silicone, or rigid such as Polycarbonate/AcrylonitrileButadiene Styrene (PC/ABS). The pre-delivery chamber 5115 may be fluidlycoupled to the humidifier wick 5230 via a plurality of valves (e.g.disposed radially throughout the pre-delivery chamber 5115) configuredto open when the quantity of water in the pre-delivery chamber 5115exceeds a threshold (e.g. predetermined threshold) amount, such as about90% of the volume of the pre-delivery chamber 5115.

5.5.2.4 Humidifier Transducers

According to one aspect of the present technology, the humidifier 5000may comprise one or more humidifier transducers configured to generate asignal indicative of the sensed characteristic, such as air flow rate,pressure, temperature or humidity. Thus the humidifier 5000 may compriseone or more flow sensors 5512 (as shown in FIGS. 15A and 15B), one ormore temperature sensors (e.g. 5514_1, 5514_2, 5514_3, 5514_4 as shownin FIGS. 15A and 15B), and/or one or more humidity sensors 5516 (asshown in FIG. 16 ) as well as any number of other types of sensors. Thehumidifier 5000 may comprise a plurality of sensors located along adirection of the air flow for example, such as temperature sensors5514_1, 5514_2, 5514_3, 5514_4 as shown in FIGS. 15A and 15B.Additionally, or alternatively, the humidifier 5000 may comprise aplurality of sensors located along a transverse direction to thedirection of air flow.

It is noted that although temperature sensors (e.g. 5514_1, 5514_2,5514_3, 5514_4, 5514_5, 5514_6, 5514_7 and 5514_8) are shown to belocated on the interior of the humidification chamber 5200, one or moreof the temperature sensors may be located outside the humidificationchamber 5200, such as on the outer surface of the outer housing heatercover portion 5202 b, or as a part of the heating element 5220, or onthe inner housing 5204.

Some humidifier transducers may be located in the humidifier 5000 (e.g.heating element temperature sensor 5514_HE shown in FIG. 16 ), howeverhumidifier transducers may also be located outside of the humidifier5000 in some cases, for example in the air circuit 4170, or in thepatient interface 3000.

Suitable locations for each of the one or more humidifier transducersmay vary according to their purpose and/or algorithms which may use asinputs signals that are generated by each of the one or more humiditysensors 5516. In some cases, transducers configured to generate a signalindicative of a sensed characteristic in one of the pneumatic path, suchas the RPT device 4000, may be used to determine the sensedcharacteristics in another part of the pneumatic path, such as thehumidifier 5000.

In some forms, a measurement of a characteristic (e.g. air flow rate,pressure, temperature or humidity) obtained at a first location may beused estimate the equivalent characteristic at a second location. Forexample, a temperature measurement obtained by a first temperaturesensor located on a heating element may be used to estimate atemperature of a water retention feature (e g humidifier wick 5230) atanother location, as will be described in detail further below in thepresent specification.

5.5.2.5 Humidifier Controller 5550

In one form, the humidifier 5000 may comprise a humidifier controller5550, which may be a standalone controller or a part of the centralcontroller 4230 (as shown in FIG. 4C). The humidifier controller 5550may monitor and/or control one or more operating parameters of thehumidifier 5000 based on inputs from components such as other componentsof the humidifier 5000 and/or the RPT device 4000.

For instance, humidifier 5000 may receive inputs from such components ashumidifier transducers, input devices 4220, or memory 4260. Furthermore,the humidifier 5000 may output signals to the heating element 5220 orthe water delivery mechanism 5150.

5.5.3 Humidifier Algorithms 5600

Various humidifier algorithms 5600 and their examples (e.g. shown inFIG. 21 ) are described below. Although they are referred to as‘humidifier algorithms’, it is to be understood that these algorithmsneed not be stored in and/or executed by the humidifier 5000. The term‘humidifier algorithms’ is used herein to indicate that the algorithmsrelate to the humidifier 5000. For example, the humidifier algorithms5600 may be executed by the central controller 4230 and stored in memory4260 of the RPT device 4000. In some instances, the algorithms 5600 maybe stored and/or executed from an external computer such as a smartphonein communication with the humidifier 5000.

5.5.3.1 Humidifier Condition Determination/Fault Mitigation Algorithms

According to one aspect, the humidifier 5000 may comprise algorithmsconfigured to determine, or detect, one or more conditions of thehumidifier 5000 and/or its components. In some cases, the humidifier5000 may further comprise fault mitigation algorithms configured toameliorate, or mitigate one or more detected fault conditions.

The humidifier condition determination algorithms may detect ordetermine conditions of humidifier components such as the reservoir5110, water delivery mechanism 5150, humidifier wick 5230, heatingelement 5220 or humidifier transducers. The conditions detected ordetermined may include: water volume, such as in the reservoir 5110,water flow rate, such as from the water delivery mechanism 5150, orwater capacity and/or water content of the humidifier wick 5230.

5.5.3.1.1 Wick Condition Determination Algorithms 5610

As described above, a performance and/or suitability for use of thehumidifier wick 5230 may change over time and/or usage, for example dueto build-up of foreign matter on the humidifier wick 5230 or degradationof the humidifier wick 5230. Accordingly, the water capacity of thehumidifier wick 5230 may change, which may affect the amount ofhumidification which can be provided to the flow of air.

According to another aspect of the present technology, the humidifier5000 may comprise one or more wick condition determination algorithms5610 for determining one or more conditions of the humidifier wick 5230.The one or more conditions of the humidifier wick 5230 to be determinedmay include suitability of the wick for use, water capacity, watercontent, or remaining usable life of the humidifier wick 5230.

In some forms (e.g. a wick condition determination algorithm 5610A asshown in FIG. 22 ), a wick condition determination algorithm may receiveone or more inputs from step 5610A2 to determine one or more conditionsof the humidifier wick 5230 in step 5610A4. The one or more conditionsof the humidifier wick may be determined by comparing the inputs tothresholds such as in step 5610A3. In one example, the thresholds may beretrieved from a memory 4260, wherein the thresholds may be stored as alook-up table or a function. The thresholds may be predetermined andstored into memory 4260 by a manufacturer of the humidifier 5000.Additionally, or alternatively, the stored values in the memory 4260 maybe updated through a data communication interface 4280, or thethresholds may be retrieved directly through a data communicationinterface 4280, such as from a remote external device 4286.

The one or more inputs may include wick type data, such as: wick model,date of manufacture, wick material, wick construction, wick dimensionsand initial water capacity. The inputs may also include wick usage data,such as: date of last replacement, time of use (e.g. total), quantity ofwater evaporated using the humidifier wick 5230, number of times thatthe humidifier wick 5230 has been washed. The inputs may include anyother data which may indicate a condition and/or a property of thehumidifier wick 5230. Yet further, the wick condition determinationalgorithms may receive inputs in some cases relating to ambientconditions. A wick condition determination algorithm may then determineone or more conditions of the humidifier wick 5230 based on one or moreof the above inputs.

Some of the wick conditions may be measured/determined and used asfurther inputs to other wick conditions. For example, wick conditionssuch as water capacity and/or the water content of the wick may bedetermined, and used as inputs to determine other wick conditions suchas a remaining usable life of the humidifier wick 5230 or to determinewhether the wick may be suitable for use, as shown in step 5610A5 ofFIG. 22 . If the humidifier wick 5230 is determined to be no longersuitable for use, the wick condition determination algorithm 5610 maygenerate a corresponding signal (e.g. in step 5610A6), for example tothe humidifier controller 5550 so that the humidifier 5000 maycommunicate to the user of a need to change the humidifier wick 5230,e.g., via a visual and/or an audible communication device.

In one example, a set of input values of: wick model, wick material,wick construction, time of use and number of times that the humidifierwick has been washed may be compared to a set of reference values (e.g.a look-up table) to determine a condition set of the wick, such as aremaining useful life of the wick and/or a water capacity of the wick.The determined condition set (e.g. a remaining useful life of the wickand/or a water capacity of the wick) may then be compared to a threshold(e g minimum remaining useful life of the wick or a minimum watercapacity of the wick) to generate a signal to indicate whether thehumidifier wick 5230 is suitable for use in the humidifier 5000. Avisual and/or an audible communication device may be provided tocommunicate to the user whether the humidifier wick 5230 is suitable foruse in the humidifier 5000. As described above, the thresholds may bepredetermined and stored into a memory 4260 for example by amanufacturer of the humidifier 5000 based on characterisation of one ormore available types of humidifier wick 5230.

In some cases, a calibration algorithm may add to or modify thethresholds, such as to be able to indicate when a humidifier wick 5230has been replaced or washed, for example based on an increase in itswater capacity.

A wick condition determination algorithm 5610 may determine and/orexpress a water capacity of the humidifier wick 5230 in absolute termsor relative terms, for example, as shown in an example algorithm 5610Bshown in FIG. 23 . That is, the water capacity of the humidifier wick5230 may be determined and/or expressed as an absolute quantity of water(e.g. in millilitres) that the humidifier wick 5230 is able to hold (asshown in step 5160B3 of FIG. 23 ) or as a relative (e.g. as apercentage) quantity (as shown in optional step 5160B5 of FIG. 23 ),such as in relation to a predetermined water capacity of the humidifierwick 5230 (as shown in input step 5160B4 of FIG. 23 ), or in relation toa minimum water capacity of the humidifier wick 5230 (not shown). Thewater capacity of the humidifier wick 5230 may be assessed prior to use(such as in step 5610B5) to determine whether the humidifier wick 5230is suitable for use, for example, by comparing the determined watercapacity to a threshold water capacity. In some forms, the wickcondition determination algorithm 5610 may indicate an unsuitability ofthe wick (step 5610B7) based on the determined water capacity of thehumidifier wick 5230.

In one form, a wick condition determination algorithm 5610 may determinea water content of the humidifier wick 5230 as a proportion of its watercapacity. The wick condition determination algorithm 5610 may in someforms indicate when a wick saturation condition is reached, which is tosay that the full water capacity of the humidifier wick 5230 has beenmet and/or exceeded. A visual and/or an audible communication device maybe provided to communicate to the user when a wick saturation conditionis reached. In some cases, determination of wick saturation may be usedas an input to another humidifier algorithm, for example to stop, orslow down, operation of the water delivery mechanism 5150.

In another aspect, the wick condition determination algorithm maydetermine a remaining life of the humidifier wick 5230 based on thecurrent water capacity of the humidifier wick 5230 and the rate ofchange of the water capacity of the humidifier wick 5230 according toone or more previously measured water capacity values of the humidifierwick 5230.

In one form (e.g. shown in FIG. 24 ), a wick condition determinationalgorithm 5610 may determine a condition of the humidifier wick 5230based on one or more temperatures (e.g. measured or sensed) at or nearthe humidifier wick 5230 (in step 5610C2). In some cases, the one ormore temperatures may be compared with reference values (in step5610C3), which may be expected temperatures, temperatures measured fromnearby sensors, or previously measured temperatures, to determine thecondition of the humidifier wick 5230 (in step 5610C4). The expectedtemperatures may be based on one or more of operating parameters of thehumidifier 5000, such as a heat output from the heating element 5220, aflow rate of air through the humidifier 5000, and a water flow ratethrough the water feed inlet 5206, as well as any number of others. Insome forms, the reference values (e.g. expected temperatures) may bedetermined from one or more look-up tables or equations based on the oneor more operating parameters. The reference values may be expressed asabsolute values (e.g. 30 degrees C.) or in relation to measured orsensed values (e.g. plus or minus 10 degrees C.).

According to another aspect, the one or more temperatures may bemeasured and/or analysed relative to each other, for instance based onany temporal or spatial patterns. In one form, measures of temperaturein a humidifier 5000 at various temperature sensors such as 5514_1,5514_2, 5514_3, 5514_4 (see FIGS. 15A and 15B) may be measured andcompared to each other, such as to determine temperature gradients overtime and/or space. In another form, measures of temperature in ahumidifier 5000 at a temperature sensor such as 5514_1 may be comparedagainst another measure at the same temperature sensor 5514_1 which wastaken at another time. For instance, an analysis may compare rates ofchange of the one or more temperatures against reference values (e.g. ofrates of change of temperatures). Alternatively, or additionally, aspatial distribution of temperatures, for example of the one or moretemperatures relative to each other, may be compared against referencevalues.

In one form, one or more of the operating conditions of the humidifier5000 may be varied while monitoring a response of one or moretemperatures to determine a condition of the humidifier 5000. Examplesof operating conditions to be varied may include a heat output from theheating element 5220, an air flow rate through the humidifier 5000, anda water flow rate through the water feed inlet 5206 as described above.However, the operating conditions may include any number of otherparameters. For example, a first set of temperatures may be measured ata set of temperature sensors, and a second set of temperatures may bemeasured at the set of temperature sensors while a heat output from theheating element 5220 is increased, to determine an increase oftemperature and/or a rate of increase of temperature for the increase inthe heat output. Then, a suitability of the humidifier wick may bedetermined based on the relationship between the increase of temperatureand/or the rate of increase of temperature and the increase in the heatoutput, for example by determining a water capacity of the humidifierwick 5230.

One arrangement of the humidifier 5000 comprising temperature sensors5514_1, 5514_2, 5514_3 and 5514_4 is shown in FIGS. 15A and 15B. In thisarrangement, measured temperatures and reference values may be obtainedat one or more of the temperature sensors 5514_1, 5514_2, 5514_3 and5514_4 to determine a condition of the humidifier wick 5230. In oneexample, a set of temperatures may be measured at one or more of thetemperature sensors 5514_1, 5514_2, 5514_3 and 5514_4 and used as a setof input values indicative of a condition of the humidifier wick 5230.Then, a set of reference values may be determined at temperature sensors5514_1, 5514_2, 5514_3 and 5514_4 for example by measurement ordetermining an expected set of temperatures.

In one example where an expected set of temperatures is used, measuredtemperatures at temperature sensors 5514_1, 5514_2, 5514_3 and 5514_4may be 40° C., 41° C., 40° C. and 52° C. respectively, while theexpected temperatures may be 40° C., 40.5° C., 41° C. and 41.5° C., at aparticular water flow rate (e.g. 1 g/min) for a particular heat input(e.g. 20 W) to the humidifier wick 5230. In this case, a wick conditiondetermination algorithm 5610 may determine that the water flow rate issufficiently high so that the humidifier wick 5230 should be wet aroundthe temperature sensor 5514_4, and thus determine the humidifier wick5230 to have a reduced water capacity around the temperature sensor5514_4.

Another exemplary arrangement of the humidifier 5000 is shown in FIG.15A. The humidifier 5000 may comprise one or more of a temperaturesensor 5514_6 positioned proximal to the water feed inlet 5206, atemperature sensor 5514_7 positioned proximal to the trailing edge ofthe humidifier wick 5230, and a temperature sensor 5514_8 at anintermediate location between the water feed inlet 5206 and the trailingedge of the humidifier wick 5230.

As water is delivered to the humidifier wick 5230 through the water feedinlet 5206, the area of the humidifier wick 5230 that is proximal to thewater feed inlet 5206 is the first area to be wetted by the waterdelivered to the humidifier wick 5230. Accordingly, a temperature sensor5514_6 may be located towards the water feed inlet 5206 to generate asignal indicative of water content in the humidifier wick 5230. If thesignal generated by the temperature sensor 5514_6 indicates the regionproximate to the temperature sensor 5514_6 to be dry, a fault conditionmay be triggered. For example, such a signal may indicate that the waterdelivery mechanism 5150 is not operating correctly, or that thehumidifier wick 5230 may require replacement.

One or more of the signals generated by the temperature sensors 5514_6,5514_7, and 5514_8 may indicate a condition of the humidifier wick 5230.In one form, a comparison of temperatures measured by the temperaturesensors 5514_6, 5514_7, and 5514_8 may be used to determine a conditionof the humidifier wick 5230 in a region around each of the respectivetemperature sensors.

In another arrangement of the humidifier shown in FIG. 16 , atemperature sensor 5514_5 may be placed at or near a periphery of thehumidifier wick 5230. For example, the temperature sensor 5514_5 may beplaced at a periphery of the humidifier wick 5230 furthest from thewater feed inlet 5206 to indicate wick saturation where a wicking rateof the humidifier wick 5230 is isotropic. In an arrangement of thehumidifier wick 5230 where the liquid wicking rate is anisotropic, thetemperature sensor 5514_5 may be placed at a periphery of the humidifierwick 5230 which may be the last periphery to be reached by the liquidbeing delivered from the water feed inlet 5206. A region of thehumidifier wick 5230 would be expected to exhibit different behavioursbetween when the region is wet in comparison to when the region is dry.Thus a behaviour at the region of the humidifier wick 5230 may bemonitored to determine whether it contains water.

A wick condition determination algorithm (e.g. example algorithm 5610C)may be configured to monitor the temperature at the sensor 5514_5, todetermine a flooded condition (in step 561005) for the region of thesensor 5514_5. When the sensor 5514_5 is located at a furthest peripheryof the humidifier wick 5230 from the water feed inlet 5206, a floodedcondition at the sensor 5514_5 may indicate a flooded condition for theentire humidifier wick 5230. Thus, for example, if a temperaturemeasured at the sensor 5514_5 is at or below a predetermined threshold,such as 2° C.-5° C. or more below a temperature of the heating element5220, the humidifier wick 5230 may be deemed to be flooded, orsaturated, by the wick condition determination algorithm 5610. In oneform, the wick condition determination algorithm 5610 may determine awater capacity of the humidifier wick 5230 by measuring a time for thehumidifier wick 5230 to be saturated. Other sensors which may besuitable for use to indicate wick saturation may include an ultrasonicsensor, a noise sensor, a condensation sensor and/or an image processingsensor. In some instances, where the wick is determined to be flooded,the water delivery mechanism 5150 may be stopped (in step 561006), andotherwise the water delivery mechanism 5150 may be continued to operate(in step 561007).

A temperature (e.g. at or near the humidifier wick 5230) may beindirectly determined, without direct measurement. In one form, ameasurement taken from a temperature sensor at a first location may beused to determine (e.g. by estimation) a temperature at a secondlocation. For example, a temperature at a first location may becorrelated to a temperature at a second location (e.g. by way of afunction or a look-up table), in which case measurement of a temperatureat the first location may allow estimation of a temperature at thesecond location (or vice versa). The correlation (e.g. function orlook-up table) may be stored in (and retrieved from) a memory 4260, andmay be predetermined such as by a manufacturer of the humidifier 5000.In one form, the correlation stored in memory 4260, may be updated forexample through a data communication interface 4280.

Thus, a wick condition determination algorithm 5610 may be configured todetermine a condition of the humidifier wick 5230 based on one or moretemperatures at or near the humidifier wick 5230, wherein the one ormore temperatures are indirectly determined.

In another form, the wick condition determination algorithm maydetermine a remaining life of the humidifier wick 5230 based on one ormore mechanical properties of a humidifier wick 5230. The one or moremechanical properties may include noise/vibration characteristics suchas a muffling or an acoustic profile. In other forms, a magnetic and/oroptical characteristic of the humidifier wick 5230 may be used todetermine a remaining life of the humidifier wick 5230.

In some forms, a wick condition determination algorithm 5610 may produceone or more outputs to be used by another humidifier algorithm. Forinstance, the wick condition determination algorithm 5610 may outputwater capacities of various zones of the humidifier wick 5230. Where ahumidifier wick 5230 is determined to have a reduced water capacity inone zone, and the heating element 5220 comprises a plurality of heatingzones, a heat output by the heating element 5220 to the correspondingheating zones may be varied according to the condition of the humidifierwick.

5.5.3.1.2 Plausibility Check Algorithms 5620

According to another aspect, the humidifier may comprise one or moreplausibility check algorithms 5620 configured to test for errors inoperation of the humidifier 5000, such as performance of one or moreindividual components of the humidifier 5000 and/or the entirehumidifier 5000.

An example plausibility check algorithm 5620A (shown in FIG. 25 ) mayreceive as inputs inlet and/or ambient conditions (step 5620A2), such asmeasures of a temperature at the air inlet 5002, humidity at the airinlet 5002, ambient temperature, and ambient humidity. The plausibilitycheck algorithm 5620A may further receive as inputs operating parameters(step 5620A3) of the humidifier 5000 such as a heat output of theheating element 5220 to the humidifier wick 5230 and a flow rate ofwater to the humidifier wick 5230. The plausibility check algorithm5620A may determine predicted output conditions (e.g.humidity/temperature at outlet, as shown in step 5620A4) based on theinputs. In one form, the plausibility check algorithm 5620 may monitoroutlet conditions (step 5620A5), such as a measured temperature at theair outlet 5004 and a measured humidity at the air outlet 5004. Theplausibility check algorithm may compare the measured temperature and/orhumidity against the predicted humidity/temperature at the outlet totest plausibility of the measured temperature and/or the humidity. Ifthe temperature at the air outlet 5004 and/or the humidity at the airoutlet 5004 is found to be implausible (step 5620A6), for example, asthey deviate more than a threshold amount from a predicted value thereofrespectively, the plausibility check algorithm may indicate a faultcondition. It is noted that in other forms of the plausibility checkalgorithm 5620, inputs, predicted values and measured values may bevaried from the examples provided above. Other examples of suitableoutput conditions to be monitored may include a temperature of thehumidifier 5000, such as a temperature at or near the humidifier wick5230. For example (not shown), the inlet/ambient conditions and outletconditions may be monitored to determine predicted operating parameters,and to compare the predicted operating parameters with measuredoperating parameters in order to determine plausibility of themeasurements.

For instance, at an absolute ambient humidity of 10 milligrams per litre(mg/L), at an air flow rate of 35 L/min, a predicted absolute humidityof the flow of air at the air outlet 5004 may be 30 mg/L. Accordingly,if the water delivery mechanism 5150 has been delivering a water flowrate of 700 mg/min, evaporation of the delivered water would add (700mg/min)/(35 L/min)=20 mg/L of absolute humidity to the flow of air atthe air outlet 5004. However, after a threshold period of time, forexample 5 minutes, the absolute humidity at the air outlet 5004 is belowa threshold amount of the target absolute humidity, the plausibilitycheck algorithm may determine that the humidifier 5000 is not operatingcorrectly and indicate a fault condition.

In another form, a plausibility check algorithm 5620 may perform a testcycle to check operation of the humidifier 5000. For instance, theplausibility check algorithm 5620 may change the heat output of theheating element 5220 and/or the water flow rate of the water deliverymechanism 5150 and check a response of the humidifier 5000 using one ormore of the humidifier transducers.

In another form, a plausibility check algorithm 5620 may check forcorrect performance of a component such as a water delivery mechanism5150, by comparing a water flow rate in comparison to a rate of movementof the water pump 5152.

The plausibility check algorithms 5620 may be configured to run at oneor more of predetermined intervals, predetermined triggers oruser/patient requests. For example, the plausibility check algorithm5620 may be performed at start-up of the humidifier 5000, at monthlyintervals, at requests of the patient 1000, at requests from a remotelocation such as a health care provider's computer, or when the humiditysensor 5516 detects that the output humidity from the humidifier 5000 isbelow a target for a threshold period of time. In other cases, theplausibility check algorithms 5620 may be configured to be runningcontinuously (or periodically) while the humidifier 5000 is inoperation.

5.5.3.1.3 Pump Condition Determination Algorithms 5630

In one form, the humidifier 5000 may comprise one or more pump conditiondetermination algorithms 5630. The pump condition determinationalgorithm may determine, for example, any blockages in the pump 5152 orany fault conditions of the pump 5152 such as an over-temperaturecondition, an over-current condition or leak. In one form, pumpcondition determination algorithm(s) may be performed at humidifierstart-up (e.g. prior to commencement of therapy and/or humidification)to determine the suitability of the pump 5152 for operation.

In one example, the pump condition determination algorithm 5630 maymonitor power consumed by the pump 5152, such as by monitoring currentconsumed by the pump 5152, and indicate a fault condition if the powerconsumed by the pump 5152 is outside of a threshold, such as a thresholdrange. In another example, the pump condition determination algorithm5630 may monitor a temperature of the pump 5152, and indicate a faultcondition if the temperature of the pump 5152 is outside of a threshold,such as a threshold range.

5.5.3.1.4 Fault Mitigation Algorithms

One aspect of the present technology relates to use of fault mitigationalgorithms

In one form, a fault mitigation algorithm may be configured to respondto outputs of wick condition determination algorithm 5610 and/or theplausibility check algorithms 5620. For instance, the wick conditiondetermination algorithm 5610 may determine a condition of the humidifierwick 5230 and output a signal indicating that the humidifier wick 5230may no longer be suitable for use. Then, the fault mitigation algorithmmay act to reduce a flow rate of air through the humidifier 5000, reducea water flow rate from the water delivery mechanism 5150, and/orpossibly stop operation of the humidifier 5000 and/or the RPT device4000.

A fault mitigation algorithm may be additionally, or alternatively,configured to respond to detection of over-temperature and/orover-current in one or more electrical components of the humidifier5000. For example, the fault mitigation algorithm may receive a signalfrom a pump condition determination algorithm 5630 that the pump ismalfunctioning, and shut down operation of the humidifier 5000.

In another form, a fault mitigation algorithm may look for a conditionwhere ‘negative leak’ is detected. Negative leak condition occurs whenthe flow rate of air through the pressure device 4140 is less than theestimated flow rate through the vent 3400 that was determined assumingnormal operating conditions. Occurrence of such a condition may indicatethat the flow rate through the vent 3400 has been reduced, for examplebecause the vent 3400 has been at least partially occluded. Onepotential cause of the blocking may be due to accumulation ofcondensation on or near the vent 3400, and accordingly the faultmitigation algorithm may reduce a level of humidification output inorder to try to reduce the occlusion.

5.5.3.2 Humidifier Control Algorithms

5.5.3.2.1 Humidification Algorithms 5650

According to one aspect, humidification algorithms 5650 may beconfigured to control components of the humidifier 5000 to manage thehumidity of the flow of air delivered from the humidifier 5000.

In one form, the humidification algorithm 5650 may receive as inputs oneor more target output conditions such as target output humidity ortarget output temperature, one or more ambient conditions such asambient humidity or ambient temperature, and/or one or more measuredoutput conditions such as measured output humidity or measured outputtemperature. Other possible inputs for the humidification algorithm 5650may include characteristics of an air circuit 4170 such as its length,or characteristics of the patient interface 3000 such as its type, orvent characteristics. In some cases, characteristics of the air circuit4170 and/or the patient interface 3000 may be input by a user, howeverin other cases, they may be detected by an identification module or arecognition system, such as that described in PCT ApplicationPublication No. WO 2010/091462, the entire contents of which is herebyincorporated by reference. The humidification algorithms 5650 mayfurther use as inputs one or more of a presence of a patient 1000, aflow rate of the flow of air through the air circuit 4170, a pressuregradient of the flow of air, or a breath rate of a patient 1000.

The humidification algorithms 5650 may in one form operate so that theflow of air delivered by the humidifier 5000 is at or close to 100%relative humidity, although other relative humidities may be possible,such as (but not limited to) 40%, 50% 60%, 70%, 80% or 90%. Oneadvantage of the present technology may include a shortened responsetime as described above. In some forms, the humidification algorithms5650 may have a target set as an absolute humidity, while in others thetarget may be set as a relative humidity. The humidification algorithm5650 may thus be configured in some forms to operate to humidify the airflow until a 90%-100% output relative humidity is detected, at whichpoint the humidification algorithm 5650 may reduce, or cease, addinghumidity (humidity output) by the humidifier 5000. Advantageously, ashortened response time of the present technology may allow thehumidifier 5000 to operate in this fashion without producingsignificant, or any, condensation, whereas a humidifier 5000 with alonger response time may not be able to reduce the humidity output inthe time required. Additionally, or alternatively, a humidificationalgorithm 5650 may reduce (or prevent) occurrence of condensation byincreasing a heat output of the air circuit heating element 4171 whenoccurrence of condensation is detected (e.g., by an optical sensor orother sensor, or methods described elsewhere in this document). Thus, inone example, where occurrence of condensation is detected, ahumidification algorithm 5650 may reduce a humidity output of thehumidifier 5000 to reduce the absolute humidity of air flow beingdelivered, while the air circuit heating element 4171 increases its heatoutput into the air circuit 4170 to ameliorate formation of furthercondensates and vaporise existing condensates.

Thus, in one form, the humidifier 5000 may be configured to maintain orincrease a humidity output until condensation is detected, for examplein the air circuit 4170, the patient interface 3000 or in the patient'sairways. Upon detection of condensates, the humidifier may decrease thehumidity output until the condensates can be said to have evaporated, orhave been removed, and no further condensates occur. Using such amethod, the humidifier 5000 may deliver a humidity as close to 100% aspossible without producing significant condensations, thereby minimisingdisturbances to the patient while improving the patient's quality oftherapy and/or comfort.

In one form, a humidification algorithm 5650 may receive as an input anoutput from a condensation detection algorithm 5700, which is describedin further detail below. The humidification algorithm 5650 may beconfigured to reduce a humidity output of the humidifier 5000 where thecondensation detection algorithm 5700 indicates an occurrence ofcondensation. Such an arrangement may be advantageous where condensationhas occurred within an air circuit 4170 away from a humidity sensor5516, in which case the humidity sensor 5516 may indicate a humidity ofless than 100% even though it may be 100% at the location ofcondensation.

In another form, an output indicating an occurrence of condensation fromthe condensation detection algorithm 5700 may be used to predict (and/orprevent) condensation to occur at a later time. For example, ifcondensation was detected at a particular time, the humidificationalgorithm 5650 may record one or more variables such as: ambientconditions (temperature/humidity/pressure), respiratory treatmentparameters (e.g. pressure, flow rate), and humidifier/air circuitoperating conditions (e.g. heating element 5220 output, measuredhumidity or measured temperature). The humidification algorithm 5650 maythen flag or learn the set of recorded variables to indicate acondensation onset condition, and predict an occurrence of condensationif a set of variables at a later time approaches the condensation onsetcondition. The humidification algorithm 5650 may then, for example,alert the user (e.g. patient 1000), or modify an operation of thehumidifier 5000 to avoid arriving at the condensation onset conditionby, for example, reducing a water flow rate from the reservoir 5110 tothe humidification chamber 5200.

According to another aspect, a humidification algorithm may beprogrammed to behave in a non-linear fashion as a response to a changein operating conditions. For instance, the humidification algorithm maybe programmed so that when a mask leak increases, e.g. from 5 L/min to10 L/min, increasing the total flow rate from 35 L/min to 40 L/min, theheat output from the heating element 5220 and the water flow rate fromthe water delivery mechanism 5150 is increased by a greater amount than5/35. In another example, the humidification algorithm may be configuredto increase the absolute humidity of the air flow when a flow rate isincreased. Such an arrangement may counteract any decreases in patientcomfort, for example due to increased leak and dryness. The response bya humidification algorithm based on a change in operating conditions maybe delayed in some cases.

In another aspect, the humidification algorithm 5650 may be configuredto determine suitable target conditions according to the ambientconditions, for example without the need for a user (or a patient 1000)to change the desired output condition. For instance, the humidificationalgorithm 5650 may direct the humidifier 5000 to output warmer air at ahigher humidity where the ambient conditions are colder and drier incomparison to where the ambient conditions are warmer and more humid.

In some forms of the humidification algorithm 5650, the heat output tothe humidifier wick 5230 and the water flow rate to the humidifier wick5230 may be controlled as a function of each other. For instance, wherethe heat output to the humidifier wick 5230 is limited, such as due tolow power availability, the water flow rate to the humidifier wick 5230may be reduced accordingly. Furthermore, where the water flow rate isreduced such as where the quantity of water in the reservoir 5110 islimited, the heat output to the humidifier wick 5230 may be reducedaccordingly.

In a yet further aspect, the humidification algorithm 5650 may determinetarget conditions according to one or more preferences and/ortherapeutic requirements of the patient 1000. In one form, thehumidification algorithm 5650 may receive a set of patient preferencesthrough input devices 4220. In another form, the humidificationalgorithm 5650 may learn a patient's preference from a usage pattern ofthe patient 1000 or detection of sleep quality of a patient 1000.

In one example, a breath phase of the patient may be used as an input tothe humidification algorithm 5650. For example, the humidificationalgorithm 5650 may cause the humidifier 5000 to add more humidity to theair flow for inspiration than expiration. Alternatively or additionally,the portion of the flow of air to be delivered to the patient duringinspiration may be of a higher temperature, for example by increasing anamount of heat delivered to the heating element 5220, or increasing theamount of water delivered to the humidifier wick 5230.

The humidifier 5000 may be arranged relative to the patient 1000 suchthat a portion of the flow of air will take a length of time to travelfrom the humidifier 5000 to the entrance of the patient's airways,wherein the length of time is significant in comparison to a length of abreath of a patient. The length of time may be referred to as ahumidification lag, and where the humidification lag is significant, itmay need to be considered in order to effectively deliver an air flowaccording to a patient's breath phase.

In one form, the time lag may be determined from a manual input by auser, for example by identifying one or more of a type and length of oneor more of the air circuit, the humidifier, the blower and the patientinterface. A controller, such as a central controller 4230, may thendetermine the time lag, for example by estimating the total length forthe air flow to travel between the humidifier 5000 and the patient 1000,and dividing by a speed of air. Then, the humidification algorithm 5650may be configured to output an air flow from the humidifier 5000 for apatient breath phase in advance of the patient breath phase by theamount of the time lag (t_(lag)). Thus, if the patient 1000 is expectedto begin inhalation at time t, the humidification algorithm 5650 may beconfigured to deliver the portion of air flow for inhalation to leavethe humidifier 5000 at time t-t_(lag).

In another example, a property of an air flow path through the patient1000 may be used as an input to the humidification algorithm 5650. Forinstance, a patient 1000 may change the orifices that they breathethrough according to a sleep state, such that while they are in bedfalling asleep, they may breathe primarily through their mouth, whereasthey may primarily breathe through their nose once they are asleep. Inother patients, the converse may apply, or some combination of mouth andnose breathing may apply, while breathing differently according to asleep state.

An air flow which is exhaled through the mouth of the patient 1000 maybe cooler than an air flow which is exhaled through the nose of thepatient 1000 due to the changed air flow paths. Accordingly, it may bedesirable to provide additional amounts of heat and moisture to thepatient 1000 where the air flow path is more directed through the mouthof the patient than the nose of the patient. In one form, a sleep stateof the patient 1000 may be determined, and the humidification algorithm5650 may automatically adjust a humidification setting according to thepatient's sleep state. In another form, a degree of mouth breathing maybe determined, and the humidification algorithm 5650 may automaticallyadjust a humidification accordingly.

In other forms, a patient's sleep state may be determined and used as aninput to the humidification algorithm 5650. For example, where thepatient is more likely to experience arousal, such as during rapid eyemoment (REM) sleep, the humidification level may be increased forimproved comfort. This may for example be balanced against other stagesof sleep where arousal is not as likely, during which time thehumidification algorithm 5650 may then reduce the humidification levelto increase the length of time over which humidification may be providedand/or an interval between the length of time for the reservoir 5110 tobe re-filled.

According to another aspect, the humidification algorithm 5650 may beconfigured to provide a period of higher humidity than the humidityprovided during the rest of the therapy session. For example, the periodof higher humidity may provide an output humidity of 95% humidity to thepatient for an hour while nominally a humidity output of 80% is providedfor the remaining hours (e.g. 7 hours) of patient's therapy (e.g. duringa night's sleep).

The period of higher of humidity may be triggered based on one or morefactors, such as mask leak, mouth leak, at humidifier start-up, towardsan end of the therapy session, a physiological state (e.g. diseasestate, allergies, fatigue level) of the patient or an environmentalfactor (e.g. pollen count).

5.5.3.2.2 Humidifier Calibration Algorithms 5660

In some cases, one or more humidifier calibration algorithms 5660 may beused to verify operation of the humidifier 5000 and/or to calibrate thehumidifier 5000. One or more humidifier calibration algorithms may beperformed periodically, or according to triggers such as user requests.For instance, an out-of-calibration operation of the humidifier 5000 maylead to an oversupply of water in comparison to the desired water flowrate, which may lead to introduction of water in the air circuit 4170.Alternatively, an undersupply of water in comparison to the desiredwater flow rate may lead to overheating of the humidifier 5000 ordiscomfort for the patient 1000.

In one form, a humidifier calibration algorithm 5660 may deliver a knownwater flow rate to a humidifier wick 5230, while varying a heat outputto the humidifier wick 5230 to analyse one or more responses of thehumidifier 5000, for example, using the humidifier transducers.

In another form, a humidifier calibration algorithm 5660 may deliver aknown heat output to a humidifier wick 5230, while varying a water flowrate to the humidifier wick 5230 to analyse one or more responses of thehumidifier 5000, for example, using the humidifier transducers.

5.5.3.2.3 Humidifier Start-Up Algorithms 5665

In some forms, one or more humidifier start-up algorithms 5665 may beused to control one or more aspects of the humidifier 5000 in itsstart-up phase of operation, for example, within the first 5, 10, 30, or60 minutes after the humidifier 5000 is switched on or after thehumidifier 5000 begins to humidify the air flow.

According to one aspect, a humidifier start-up algorithm 5665 may beconfigured to initiate operation of a first component prior to a secondcomponent during the start-up phase, while both the first and the secondcomponents may simultaneously operate subsequent to the start-up phase.In one form, the humidifier start-up algorithm 5665 may initiateoperation of the water delivery mechanism 5150 prior to initiatingoperation of the heating element 5220 to prevent overheating.

In one example, the humidifier start-up algorithm 5665 may be configuredto delay supply of power to the heating element 5220 until the waterdelivery mechanism 5150 has delivered at least a predetermined amount ofwater to the humidifier wick 5230, which may be measured in relativeterms (such as 20%, 40%, 60%, 80% of wick saturation) or in absoluteterms (such as 2.5 g, 5 g, 10 g, or 15 g of water). In another form, thehumidifier start-up algorithm 5665 may be configured to delay supply ofpower to the heating element 5220 by a predetermined length of time,such as 15 seconds, 30 seconds, 1 minute, or 2 minutes to allow for thehumidifier wick 5230 to receive a volume of water from the waterdelivery mechanism 5150. In yet other forms, the water deliverymechanism 5150 and the heating element 5220 may simultaneously beinitiated, however, the power supplied to the heating element 5220 maybe reduced during the start-up phase.

According to another aspect, a humidifier start-up algorithm 5665 may beconfigured to provide an increased humidity output during the start-upphase. In one form, the humidifier start-up algorithm 5665 may beconfigured to provide more power to the heating element 5220 and/orhigher water flow rate through the water delivery mechanism 5150 thanthe power and/or water flow rate used throughout a subsequent timeperiod.

For example, the humidifier start-up algorithm 5665 may be configured sothat the power output by the heating element 5220 may be higher duringthe start-up phase than a subsequent time period or phase. For example,the power output by the heating element 5220 may be approximately 20%,approximately 40%, approximately 60%, or approximately 80% higher than apower output by the heating element 5220 in its normal operation.

Alternatively, or additionally, the water flow rate from the waterreservoir 5110 to the humidifier chamber 5200, such as by the waterdelivery mechanism 5150, may be increased together with, orindependently of, the power provided to the heating element 5220.

Thus, the humidity and/or heat output by the humidifier 5000 may behigher at a start-up phase in comparison to the subsequent time periodor phase. Accordingly, the air flow delivered to the patient may beconditioned to the desired humidity/or temperature at a faster speedthan if the humidity and/or heat output by the humidifier 5000 hadstayed constant. Alternatively, or additionally, in some cases, the airflow delivered to the patient may be at an increased humidity and/ortemperature during the start-up phase, which the patient may find moredesirable, before settling to a decreased level of humidity and/ortemperature during a subsequent time period or phase.

5.5.3.2.4 Foreign Matter Management Algorithms 5670

As described above, formation, collection, and/or build-up on foreignmatter such as particulates may occur on the humidifier wick 5230, whichmay adversely affect a performance of the humidifier wick 5230.According to one aspect, one or more foreign matter managementalgorithms may be used to control the location and/or rate of foreignmatter build-up on the humidifier wick 5230.

In some cases, foreign matter may collect on the humidifier wick at thegreatest rate where the humidifier wick 5230 dries out completely. Forinstance, at a water boundary 5230_WB of the water retained by thehumidifier wick 5230, as shown in FIGS. 14A and 14B. In one form, aforeign matter management algorithm 5670 may manage a location and/orpattern of a water boundary 5230_WB, for example, away from an area ofdetected low water capacity. The foreign matter management algorithm5670 may achieve this goal by controlling one or more of the heat outputonto the humidifier wick 5230, a water flow rate onto the humidifierwick 5230 or a water distribution pattern within the humidifier wick5230.

According to another aspect, a foreign matter management algorithm maybe configured to determine a quality of water, such as a foreign mattercontent in the water. In one form, a conductivity of water may bemeasured to determine the foreign matter content in the water. In oneform, electrodes in contact with the water may be placed in thehumidifier 5000 (e.g. in the reservoir 5110, water delivery mechanism5150, or in the humidifier wick 5230) to measure resistivity of thewater. In some forms, the electrodes may be placed in the humidifierwick 5230 so that the resistivity measured will indicate resistivity ofthe wick and the water therein, where a high resistivity may indicate acorresponding high level of foreign matter build-up in the wick.

The foreign matter management algorithm may be configured to vary alocation of the water boundary 5230_WB during use of the humidifier5000. Particulates or foreign matter may collect at a faster rate at thelocation of the water boundary 5230_WB than the rest of the humidifierwick 5230. Thus, during use of the humidifier 5000, by varying alocation of the water boundary 5230_WB, a distribution of the foreignmatter that is collected throughout the humidifier wick 5230 may becontrolled, for example to extend a useful life of the humidifier wick5230.

The foreign matter management algorithm may vary a location of the waterboundary 5230_WB by adjusting one or both of the water flow rate to thehumidifier wick 5230 and a heat output of the heating element 5220.

In one form, a water flow rate of the humidifier 5000 may be variedbetween a minimum water flow rate and a maximum water flow rate. Thewater flow rate may vary between the minimum water flow rate and themaximum water flow rate, such as linearly or as a sinusoid for example.

A location of the water boundary 5230_WB may be varied during use of ahumidifier 5000, such as shown in FIGS. 14A and 14B. The location of thewater boundary 5230_WB may be varied in a reciprocating motion, suchthat the water boundary 5230_WB moves from a first location shown inFIG. 14A, to a second location shown in 14B, back to the first locationshown in 14A, and so on.

Alternatively, or additionally, a heat output of the heating element5220 may be varied between a minimum heat output and a maximum heatoutput. The heat output may vary between the minimum heat output and themaximum heat output, such as linearly or as a sinusoid for example.

It will be understood by the skilled person that a number of other meansmay also be used to vary a location of the water boundary 5230_WB. Itwill be also understood that the variation of a location of the waterboundary 5230_WB may follow a different regime, such as at a non-linearrate.

In some forms, variation of the location of the water boundary 5230_WBmay be periodic, to encourage a build-up of particulates to occuraccording to an even distribution through a length of the humidifierwick 5230.

In some forms, the foreign matter management algorithm may be configuredsuch that a location of the water boundary 5230_WB may be at leastpartly determined by a determined condition of the humidifier wick 5230.For example, a first region of the humidifier wick 5230 may be found toinclude a higher concentration of foreign matter or particulates than asecond region of the humidifier wick 5230. In response, the foreignmatter management algorithm may operate to move the water boundary5230_WB towards, or into the second region for longer periods of timethan in the first region.

5.5.3.2.5 Wick Drying Algorithms 5675

The humidifier 5000 may comprise one or more wick drying algorithms 5675configured to reduce a water content of a humidifier wick 5230. A wickdrying algorithm 5675 may operate to dry the humidifier wick 5230, suchas at completion of a therapy session, or when the humidifier wick 5230is determined to be saturated with water.

A wick drying algorithm 5675 may reduce a water content of thehumidifier wick 5230 by one or more of: preventing a flow of liquid fromthe reservoir 5110 to the humidifier wick 5230, reducing a flow ofliquid from the reservoir 5110 to the humidifier wick 5230, increasing aheat output of the heating element 5220, increasing a flow rate of airthrough the humidifier 5000, and increasing a temperature of the airthrough the humidifier 5000.

5.5.3.2.6 Wick Cleaning Algorithms 5680

The humidifier 5000 may comprise one or more wick cleaning algorithms5680 configured to clean the humidifier wick 5230, for reducing theamount of foreign matter and/or any bio-burden on the humidifier wick5230.

In one form, a wick cleaning algorithm 5680 may operate to rinse thehumidifier wick 5230 with a supply of water and/or a cleaning agent.Additionally, or alternatively, the wick cleaning algorithm 5680 may drythe humidifier wick 5230, in some cases at a temperature higher than anoperating temperature.

In another form, a wick cleaning algorithm 5680 may be configured toactivate where a cleaning adapter is coupled to the humidifier 5000. Oneadvantage of this form may be to prevent use of the humidifier 5000 bythe patient 1000 while the wick cleaning algorithm 5680 is activated. Insome cases, the cleaning adapter may comprise a cleaning agent which maybe released into the humidifier wick 5230 while the wick cleaningalgorithm 5680 is active.

A wick cleaning algorithm 5680 may be configured to operate in someforms after cessation of therapy. In some cases, the RPT device 4000and/or a humidifier 5000 may be arranged with a battery to enableoperation of the wick cleaning algorithm 5680 after power has beenswitched off.

5.5.3.3 Patient Feedback Algorithms 5690

The humidifier 5000 may comprise one or more patient feedback algorithms5690 for relaying information and/or providing recommendations to thepatient 1000.

Patient feedback algorithms 5690 may, in some forms, inform the patient1000 of one or more outputs from the humidifier algorithms describedabove. Examples of information provided to a patient 1000 by a patientfeedback algorithm 5690 may include a condition of the humidifier wick5230, such as its remaining life or a quality of the water, or anyanomalous activity of the humidifier 5000, or an indication of a fault,such as detection of a missing reservoir 5110. In some cases, a patientfeedback algorithm 5690 may simply indicate to a patient 1000 or acaregiver that the humidifier wick 5230 may require washing.

In one form, a patient feedback algorithm 5690 may collect data relatinga patient's sleep data to one or more humidification conditions. Thepatient feedback algorithm 5690 may then correlate the measured data todetermine one or more preferred humidification conditions. For example,the patient feedback algorithm 5690 may collect patient sleep datarelating to one or more of: arousal event data, sleep state data and anySDB event data. The patient feedback algorithm 5690 may also collect oneor more humidification conditions such as ambient conditions (e.g.ambient temperature, pressure, humidity) and/or output conditions(output temperature, humidity), and correlate the patient sleep data tohumidification conditions to determine the patient's preferred outputtemperature and/or humidity based on ambient conditions.

A patient feedback algorithm 5690 may also include as inputs one or moreof: therapy conditions (e.g. total flow rate, leak flow rate, therapypressure), sleep disordered breathing events (e.g. apneas, hypopneas,arousals, flow limitations), calendar data (e.g. distinguish betweenweekday/weekend, first scheduled meeting of the day, alarm clocksetting), and a sleep state monitor to determine the output temperatureand/or humidity to be delivered to the patient by correlating the inputsto a preferred humidification condition.

5.5.3.4 Condensation Related Algorithms

5.5.3.4.1 Condensation Detection Algorithms 5700

Occurrence of condensation in a respiratory treatment system may beundesirable as condensation may adversely affect operation of one ormore components. For example, condensates may short circuit anelectrical connection, or occlude a pneumatic path such as a vent 3400or a port of a transducer such as a flow transducer 4274 or a pressuretransducer 4272. Condensation, when it occurs in significant quantities,may also affect the patient 1000 in that ingress of condensation intothe patient's airways during sleep may cause disturbances such asarousal, or worse, potentially present a hazard. Thus, the humidifier5000 may comprise one or more algorithms to determine whethercondensation may have occurred in the respiratory treatment system.

According to a first example, a condensation detection algorithm 5700may be configured to compare properties of the air flow at a firstlocation and a second location to determine whether any condensation mayhave occurred therebetween.

In one form (see FIG. 26 ), a respiratory treatment system (e.g. in thehumidifier 5000 or the air circuit 4170) may comprise a first humiditysensor 5516_1 (e.g. at or near an inlet of an air circuit 4170), and asecond humidity sensor 5516_2 downstream of the first humidity sensor(e.g. at or near an outlet of the air circuit 4170). Occurrence ofcondensation in the air circuit 4170 may cause a decrease in absolutehumidity from the inlet to the outlet of the air circuit, as moisture isremoved from the air flow (where it is in a form of water vapour) asliquid water. Thus, a condensation detection algorithm 5700 may beconfigured to indicate an occurrence of condensation in the air circuitupon detection of a decrease in absolute humidity from the firsthumidity sensor 5516_1 to second humidity sensor 5516_2. In some forms,where the humidity sensor is configured to measure a relative humidity,the respiratory treatment system may comprise additional sensors, suchas a temperature sensor to help determine an absolute humidity.

For instance, air at the first humidity sensor 5516_1 may be determinedto have a relative humidity of 86% at a temperature of 30 degrees, and arelative humidity of 92% at a temperature of 27 degrees at the secondhumidity sensor. The corresponding absolute humidity at the firsthumidity sensor 5516_1 would be 23.2 g/kg, and 20.9 g/kg at the secondhumidity sensor 5516_2. At an air flow rate of 30 litres per minute, thecondensates would be produced between the first humidity sensor 5516_1to second humidity sensor 5516_2 at a rate of approximately 0.09 g/min,or 5.4 g/hour. Thus the condensation detection algorithm 5700 mayindicate an occurrence of condensation, which may then be used toprevent occurrence of further condensation and prevent accumulation ofcondensates.

In another example, a measured thermal response may be compared to apredicted thermal response to indicate an occurrence of condensation,where the predicted thermal response is based on an assumption of lackof condensation. Where condensation has occurred within an air circuit4170, a thermal response of the air flow in the air circuit 4170 may bealtered due to an increased heat capacity of the contents of the aircircuit 4170. For example, saturated air at a temperature of 25° C. hasa density of 1.166 kg/m3, with a heat capacity of 1.043 kJ/kgK. At anair flow rate of 30 litres per minute (0.5 litres per second), the totalheat capacity of the air flow (per second) would be 0.61 kJ/K. The heatcapacity of the contents of the air circuit 4170 would then beapproximately doubled should liquid water of 0.15 g mass be present inthe tube. Accordingly, when heat is input to the air circuit 4170,presence of condensation may reduce a heating response of the air flowtherein in comparison to a heating response where the prediction assumedthat condensates are not present in the air circuit 4170, therebychanging a measured thermal response from the predicted thermalresponse.

Thus, in one form, a condensation detection algorithm 5700 may detectoccurrence of condensation by comparing a measure of rate of heat energyinput to the air circuit 4170, and a measure of heating response, suchas heating rate per time or heating rate per distance. Referring to FIG.27 , for example, a respiratory treatment system may comprise a firsttemperature sensor 5514_6 (e.g. located at an inlet of the air circuit4170) and a second temperature sensor 5514_7 located downstream of thefirst temperature sensor 5514_6 (e.g. at an outlet of the air circuit4170). Where the air circuit 4170 comprises a heating element 4171, theheat energy input into the air circuit 4170 (and thus to the air flowtravelling therethough) may be correlated to measurements at one or moreof the first temperature sensor 5514_6 and the second temperature sensor5514_7.

In some forms, the condensation detection algorithm 5700 may also use asinputs one or more of: a pressure or flow rate of the air flowtravelling through the air circuit 4170, ambient conditions (e.g.temperature/humidity/pressure), or a rate of heat transfer between theair circuit 4170 and the ambient. The flow rate may be determined by aflow transducer 4274 or an estimation method (e.g. as described in U.S.Pat. No. 5,740,795, the entire content of which is incorporatedherewithin by reference).

Based on the above inputs, the condensation detection algorithm 5700 maydetermine a predicted thermal response, to compare against a measuredthermal response, such as a temperature difference between twotemperature sensors (e.g. the first temperature sensor 5514_6 and thesecond temperature sensor 5514_7), or a rate of change of temperature ata temperature sensor (e.g. second temperature sensor 5514_7). In someforms, a predicted thermal response may be based on one or more previousmeasurements of thermal response.

In another form, a predicted thermal response may be based on a look-uptable or a model which is based on an assumption wherein condensates arenot present.

In one form, the condensation detection algorithm 5700 may be configuredto indicate an occurrence of condensation where the measured thermalresponse deviates from the predicted thermal response by more than athreshold. For example, when the predicted temperature difference isgreater than the measured temperature difference by a threshold, such asa predetermined percentage or a predetermined temperature. In anotherform, the condensation detection algorithm 5700 may be configured toindicate an occurrence of condensation where a predicted rate of changeof temperature (e.g. at the second temperature sensor 5514_7) is greaterthan a measured rate of change of temperature, such as a predeterminedpercentage or a predetermined magnitude.

In another example, a condensation detection algorithm 5700 maydetermine an occurrence of condensation by establishing a steady statebaseline condition, and searching for a deviation from the baselinecondition which may be caused by condensates.

In one form, the air circuit 4170 as shown in FIG. 27 may be operatingin a steady state such that temperatures measured at the secondtemperature sensor 5514_7 has been consistent for a period of time,which may be a predetermined period of time (e.g. 30 seconds, 1 minute,5 minutes, 10 minutes). In such a case, in the absence of othersignificant deviations in relevant variables, the condensation detectionalgorithm 5700 may indicate an occurrence of condensation where thetemperatures measured at the second temperature sensor 5514_7 begin todecrease, which may be caused by an increase in heat capacity of thecontents of the air circuit 4170.

It will be understood by those skilled in the art that aspects of any ofthe above examples may be combined to derive other methods of detectingan occurrence of condensation.

5.5.3.4.2 Condensation Calibration Algorithms 5710

According to one aspect, the humidifier 5000 may comprise a condensationcalibration algorithm 5710 configured to establish one or more variablesindicating a condition at which condensation may occur. A set of suchvariables may be referred to as a condensation onset condition. Forexample, a condensation calibration algorithm 5710 may monitor all orsome of: ambient pressure, ambient temperature, therapy pressure, airflow rate and air flow temperature, heat input by the humidifier heatingelement 5220, and heat input by the air circuit heating element 4171.

The humidification algorithm 5650 may use the established condensationonset condition to operate the humidifier 5000 at or near saturationhumidity. As the condensation onset condition may comprise multiplevariables, in some forms, the condensation calibration algorithm 5710may record a plurality of condensation onset conditions, any of whichmay result in the air circuit 4170 experiencing an occurrence ofcondensation. In one form, the condensation calibration algorithm 5710may be configured to operate periodically (e.g. every 10 minutes, 30minutes, 1 hours) to update the condensation onset condition(s).

In one form, a condensation calibration algorithm 5710 may operate anair circuit heating element 4171 at a plurality of power outputconditions, and monitor the thermal response. For example, thecondensation calibration algorithm 5710 may operate the air circuitheating element 4171 at one or more power outputs, for example at 30 W,25 W, 20 W, 15 W, 10 W and 5 W, and monitor a temperature gradientwithin the air circuit 4170, for example by monitoring a rate of heatingbetween two temperature sensors (e.g. first temperature sensor 5514_6and second temperature sensor 5514_7 as shown in FIG. 27 ). Theresulting rate of heating (e.g. difference in temperature between thetwo temperature sensors 5514_6 and 5514_7), may be correlated with thepower output of the heating element 4171, to determine a condensationonset condition, for example, as shown in FIG. 29 , where a condensationonset condition is found as an inflection point 5712. The conditionsbelow the inflection point may be referred to as a condensationcondition 5716, and conditions above the inflection point may bereferred to as a non-condensation condition 5714.

According to one aspect, where the air circuit 4170 may comprise aplurality of zones (as described above), a condensation calibrationalgorithm 5710 may use one of the plurality of zones to determine asaturation condition. For example, as shown in FIG. 28 , the air circuit4170 may comprise a first zone 4170_1 located distal to the patient anda second zone 4170_2 located proximal to the patient. The first zone4170_1 may be operated at a first set of parameters (e.g. at a firstrate of heat input from a first heating element 4171_1) to producecondensation therein, in order find a set of condensation onsetconditions as described above. At the same time, the second zone 4170_2may be operated at a second set of parameters (e.g. at a second, higherrate of heat input from a second heating element 4171_2) to preventoccurrence of condensation in portions of the air circuit 4170 which maybe proximal to the patient (e.g. in the second zone 4170_2).

According to one aspect, the condensation calibration algorithm 5710 maybe configured to search for one or more condensation onset conditionsindependently of an output from a condensation detection algorithm 5700.In one form, the condensation calibration algorithm 5710 may achievethis goal by changing a variable until a condensation onset conditionwas detected, such that for example condensation had ceased to occur, orcondensation had begun to occur.

For example, as shown in FIG. 30A and FIG. 30B, the condensationcalibration algorithm 5710 may vary the heating power supplied (e.g. bythe heating element 4171) to the air circuit 4170 to find condensationonset conditions. In FIG. 30A, starting from a condensation condition,the condensation calibration algorithm 5710 may increase the heatingpower supplied until a condensation detection algorithm 5700 detects acessation of condensation at, for example 5711, which may be marked as acondensation onset condition. Also, starting from a condensationcondition, the condensation calibration algorithm 5710 may decrease theheating power supplied until the condensation detection algorithm 5700detects that condensation is occurring at for example 5712, which mayalso be marked as a condensation onset condition. The actualcondensation onset condition may be somewhere between the two markedconditions 5711 and 5712, and may be shown on the graph as 5713, whichwould be a horizontal line (as shown in FIG. 30A) if the condensationonset condition remained consistent (that is, in a steady-state). If theactual condensation onset condition varies over time, for example, asshown in FIG. 30B, the condensation calibration algorithm 5710 maydetect the condensation onset condition varying over time and maycontinually update the condensation onset condition.

Accordingly, where a plurality of measured condensation onset conditionsare available, these values may be for example filtered over time (e.g.by low-pass filtering), or averaged, to estimate the actual condensationonset condition. Furthermore, the plurality of measured condensationonset conditions may be used to indicate a plausibility of measurements.For instance, the condensation calibration algorithm 5710 may beconfigured to indicate a potential fault (e.g. in the humidifier 5000 orair circuit 4170) where the measured condensation onset condition variesgreatly (e.g. where a standard deviation of the measured condensationonset conditions is above a threshold).

5.5.3.4.3 Condensation Confirmation Algorithms 5720

The humidifier 5000 may also comprise algorithms configured to confirman occurrence of condensation as determined by a condensation detectionalgorithm 5700. In one form, a condensation confirmation algorithm 5720may be triggered when a condensation detection algorithm 5700 indicatesan occurrence of condensation.

According to one aspect, a condensation confirmation algorithm 5720 maycause the humidifier 5000 to traverse the condensation onset condition,and compare a thermal response at either side of the condensation onsetcondition. For example, the condensation confirmation algorithm 5720 maydecrease a heat output of the heating element 4171 from 20 W to 10 W, if15 W was determined to be the condensation onset condition (e.g.traverse from a condensation condition 5716 to non-condensationcondition 5714 in FIG. 29 ). Conversely, the heat output of the heatingelement 4171 may be increased from 10 W to 20 W where condensation wasexpected to occur at or below 15 W output, at which point it would beexpected that no further condensation would occur.

In some cases, if an occurrence of condensation was due to a one-timeevent (e.g. introduction of moisture due to spillage by a user), or achange in an ambient condition (e.g. a blanket covering the tube beingremoved), traversing the condensation onset condition may not cause acessation (or production) of condensates. In such cases, thecondensation confirmation algorithm 5720 may be configured to continueto increase (or decrease) the heat output of the heating element 4171until the expected change in thermal response (e.g. change from acondensation condition to a non-condensation condition, or vice versa)occurs.

5.5.3.5 Heating Plausibility Algorithms 5730

According to another aspect, the humidifier 5000 may comprise one ormore heating plausibility algorithms 5730 to indicate an occurrence of apotential fault. For example, where a change in a variable has occurred,such as in an ambient temperature, output of a heating element (e ghumidifier heating element 5220 or air circuit heating element 4171) oran air flow rate, a heating plausibility algorithm 5730 may assesswhether the measured effects may be varying in a manner which may beconsistent with the change in the variable.

For instance, if the flow transducer 4274 is recording a low flow ratecondition, and one or more heating elements are heating the air flow, aheating plausibility algorithm 5730 may perform a check to assesswhether a measured temperature is expected to increase, and whether themeasured temperature is increasing in a manner consistent with theprediction. If the increase in temperature is lower than the predictedincrease, or the temperature does not increase at all, the heatingplausibility algorithm 5730 may indicate a fault condition.

In some forms, the heating plausibility algorithm 5730 may perform amitigation step such as for example reducing or ceasing power suppliedby a heating element 5220 or 4171.

5.5.3.6 Tube Detection Algorithms 5740

In one form, one or more measurements of a thermal response to a heatinput may be used to detect a parameter of an air circuit 4170, such asits length. For example, where a known amount of electrical power issupplied, the thermal response of the heated tube may differ accordingto a parameter such as length, or amount of insulation, which may beused to determine the parameter.

5.6 GLOSSARY

For the purposes of the present technology disclosure, in certain formsof the present technology, one or more of the following definitions mayapply. In other forms of the present technology, alternative definitionsmay apply.

5.6.1 General

Air: ‘Air’ in the present disclosure will be taken to include breathablegases. In certain forms of the present technology, air supplied to apatient may be atmospheric air, and in other forms of the presenttechnology atmospheric air may be supplemented with oxygen.

Ambient: In certain forms of the present technology, the term ambientwill be taken to mean (i) external of the treatment system or patient,and (ii) immediately surrounding the treatment system or patient. Forexample, ambient humidity with respect to a humidifier may be thehumidity of air immediately surrounding the humidifier.

Continuous Positive Airway Pressure (CPAP): CPAP treatment will be takento mean the application of a supply of air or air to the entrance to theairways at a pressure that is continuously positive with respect toatmosphere, and preferably approximately constant through a respiratorycycle of a patient. In some forms, the pressure at the entrance to theairways will vary by a few centimeters of water within a singlerespiratory cycle, for example being higher during inhalation and lowerduring exhalation. In some forms, the pressure at the entrance to theairways will be slightly higher during exhalation, and slightly lowerduring inhalation. In some forms, the pressure will vary betweendifferent respiratory cycles of the patient, for example being increasedin response to detection of indications of partial upper airwayobstruction, and decreased in the absence of indications of partialupper airway obstruction.

5.6.2 Aspects of RPT Devices

Air circuit: A conduit or tube constructed and arranged in use todeliver a supply of air between an RPT device and a patient interface.In particular, the air circuit may be in fluid connection with theoutlet of the pneumatic block and the patient interface. The air circuitmay be referred to as air delivery tube. In some cases there may beseparate limbs of the circuit for inhalation and exhalation. In othercases a single limb is used.

5.7 OTHER REMARKS

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent file or records, but otherwise reserves all copyrightrights whatsoever.

Unless the context clearly dictates otherwise and where a range ofvalues is provided, it is understood that each intervening value, to thetenth of the unit of the lower limit, between the upper and lower limitof that range, and any other stated or intervening value in that statedrange is encompassed within the technology. The upper and lower limitsof these intervening ranges, which may be independently included in theintervening ranges, are also encompassed within the technology, subjectto any specifically excluded limit in the stated range. Where the statedrange includes one or both of the limits, ranges excluding either orboth of those included limits are also included in the technology.

Furthermore, where a value or values are stated herein as beingimplemented as part of the technology, it is understood that such valuesmay be approximated, unless otherwise stated, and such values may beutilized to any suitable significant digit to the extent that apractical technical implementation may permit or require it.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this technology belongs. Although any methods andmaterials similar or equivalent to those described herein can also beused in the practice or testing of the present technology, a limitednumber of the exemplary methods and materials are described herein.

When a particular material is identified as being preferably used toconstruct a component, obvious alternative materials with similarproperties may be used as a substitute. Furthermore, unless specified tothe contrary, any and all components herein described are understood tobe capable of being manufactured and, as such, may be manufacturedtogether or separately.

It must be noted that as used herein and in the appended claims, thesingular forms “a”, “an”, and “the” include their plural equivalents,unless the context clearly dictates otherwise.

All publications mentioned herein are incorporated by reference todisclose and describe the methods and/or materials which are the subjectof those publications. The publications discussed herein are providedsolely for their disclosure prior to the filing date of the presentapplication. Nothing herein is to be construed as an admission that thepresent technology is not entitled to antedate such publication byvirtue of prior invention. Further, the dates of publication providedmay be different from the actual publication dates, which may need to beindependently confirmed.

Moreover, in interpreting the disclosure, all terms should beinterpreted in a manner consistent with the context. In particular, theterms “comprises” and “comprising” should be interpreted as referring toelements, components, or steps in a non-exclusive manner, indicatingthat the referenced elements, components, or steps may be present, orutilized, or combined with other elements, components, or steps that arenot expressly referenced.

The subject headings used in the detailed description are included onlyfor the ease of reference of the reader and should not be used to limitthe subject matter found throughout the disclosure or the claims. Thesubject headings should not be used in construing the scope of theclaims or the claim limitations.

Although the technology herein has been described with reference toparticular examples, it is to be understood that these examples aremerely illustrative of the principles and applications of thetechnology. In some instances, the terminology and symbols may implyspecific details that are not required to practice the technology. Forexample, although the terms “first” and “second” may be used, unlessotherwise specified, they are not intended to indicate any order but maybe utilised to distinguish between distinct elements. Furthermore,although process steps in the methodologies may be described orillustrated in an order, such an ordering is not required. Those skilledin the art will recognize that such ordering may be modified and/oraspects thereof may be conducted concurrently or even synchronously.

It is therefore to be understood that numerous modifications may be madeto the illustrative examples and that other arrangements may be devisedwithout departing from the spirit and scope of the technology.

5.8 REFERENCE SIGNS LIST

patient 1000 bed partner 1100 patient interface 3000 seal-formingstructure 3100 plenum chamber 3200 stabilising structure 3300 connectionport 3600 forehead support 3700 RPT device 4000 external housing 4010upper portion 4012 lower portion 4014 panel 4015 chassis 4016 handle4018 pneumatic block 4020 pneumatic component 4100 air filter 4110 inletair filter 4112 outlet air filter 4114 muffler 4120 inlet muffler 4122outlet muffler 4124 pressure device 4140 blower 4142 motor 4144 backvalve 4160 air circuit 4170 first air circuit zone 4170_1 second aircircuit zone 4170_2 air circuit heating element 4171 first air circuitheating element 4171_1 second air circuit heating element 4171_2supplemental oxygen 4180 electrical component 4200 PCBA 4202 powersupply 4210 input device 4220 central controller 4230 clock 4232 therapydevice controller 4240 protection circuit 4250 memory 4260 transducer4270 pressure transducer 4272 flow transducer 4274 motor speed sensor4276 data communication interface 4280 remote external communicationnetwork 4282 local external communication network 4284 remote externaldevice 4286 local external device 4288 output device 4290 display driver4292 display 4294 humidifier 5000 air inlet 5002 air outlet 5004reservoir 5110 water volume detector 5112 water delivery mechanism 5150water pump 5152 water delivery conduit 5154 mechanism 5156 water checkvalve 5158 humidification chamber 5200 outer housing 5202 outer housinginlet portion 5202a outer housing heater cover portion 5202b outerhousing outlet portion 5202c inner housing 5204 water feed inlet 5206air flow baffle 5208 water filter 5214 heating element 5220 reservoirheating element 5221 humidifier wick 5230 wick dry region 5230_D wickwet region 5230_W water boundary 5230_WB wick first layer 5230a wicksecond layer 5230b wick frame 5232 wick frame grip 5232_G wick locator5233 humidifier filter 5240 flow sensor 5512 temperature sensor 5514temperature sensor 5514_1 temperature sensor 5514_2 temperature sensor5514_3 temperature sensor 5514_4 temperature sensor 5514_5 heatingelement temperature sensor 5514_HE pre-delivery chamber 5515 humiditysensor 5516 first humidity sensor 5516_1 second humidity sensor 5516_2humidifier controller 5550 humidifier algorithm 5600 wick conditiondetermination algorithm 5610 plausibility check algorithm 5620 pumpcondition determination algorithm 5630 humidification algorithm 5650humidifier calibration algorithm 5660 humidifier start-up algorithm 5665foreign matter management algorithm 5670 wick drying algorithm 5675 wickcleaning algorithm 5680 patient feedback algorithm 5690 condensationdetection algorithm 5700 condensation calibration algorithm 5710inflection point 5712 non-condensation condition 5714 condensationcondition 5716 condensation confirmation algorithm 5720 heatingplausibility algorithm 5730 tube detection algorithm 5740 downstreamunheated region 5230D heated region 5230H upstream unheated region 5230Uexample wick condition determination algorithm 5610A example wickcondition determination algorithm 5610A1 step 1 example wick conditiondetermination algorithm 5610A2 step 2 example wick conditiondetermination algorithm 5610A3 step 3 example wick conditiondetermination algorithm 5610A4 step 4 example wick conditiondetermination algorithm 5610A5 step 5 example wick conditiondetermination algorithm 5610A6 step 6 example wick conditiondetermination algorithm 5610B example wick condition determinationalgorithm 5610B1 step 1 example wick condition determination algorithm5610B2 step 2 example wick condition determination algorithm 5160B3 step3 example wick condition determination algorithm 5160B4 step 4 examplewick condition determination algorithm 5610B5 step 5 example wickcondition determination algorithm 5610B6 step 6 example wick conditiondetermination algorithm 5610B7 step 7 example wick conditiondetermination algorithm 5610C example wick condition determinationalgorithm 5610C1 step 1 example wick condition determination algorithm5610C2 step 2 example wick condition determination algorithm 5610C3 step3 example wick condition determination algorithm 5610C4 step 4 examplewick condition determination algorithm 5610C5 step 5 example wickcondition determination algorithm 5610C6 step 6 example wick conditiondetermination algorithm 5610C7 step 7 example plausibility checkalgorithm 5620A example plausibility check algorithm step 1 5620A1example plausibility check algorithm step 2 5620A2 example plausibilitycheck algorithm step 3 5620A3 example plausibility check algorithm step4 5620A4 example plausibility check algorithm step 5 5620A5 exampleplausibility check algorithm step 6 5620A6

The invention claimed is:
 1. A humidifier for increasing moisture in aflow of air to be delivered to a patient's airways by a respiratorypressure therapy device, the humidifier comprising: a humidifier housingforming a humidification chamber, the humidifier housing comprising: anair inlet configured to receive the flow of air from the respiratorypressure therapy device; an air outlet configured to deliver the flow ofair to a patient interface from the humidification chamber with addedmoisture; and a flow path for the flow of air from the air inlet,through the humidification chamber, and to the air outlet; a humidifierwick positioned within the humidifier housing, the humidifier wick beingconfigured to retain a volume of water and the humidifier wick formingan external boundary of at least a portion of the flow path; and ahumidifier wick frame positioned radially inward of the humidifier wickand configured to maintain the humidifier wick's shape and positionwithin the humidifier housing, the humidifier wick frame being coupledto the humidifier wick such that the humidifier wick frame and thehumidifier wick are removable from the humidifier housing as a singleunit.
 2. The humidifier of claim 1, wherein the humidification chamberis substantially cylindrical in shape.
 3. The humidifier of claim 1,wherein the humidifier wick frame further comprises a grip surface forgripping the humidifier wick frame during insertion or removal of thehumidifier wick frame and the humidifier wick from the humidifierhousing.
 4. The humidifier of claim 3, wherein the humidifier wick frameis shaped and dimensioned such that a portion of the grip surfaceextends externally of the humidification chamber when the the humidifierwick frame and the humidifier wick are installed in the humidifierhousing.
 5. The humidifier of claim 3, wherein the grip surface ismarked with a color and/or an indicator for identification.
 6. Thehumidifier of claim 3, wherein the grip surface is textured for grippingduring insertion or removal.
 7. The humidifier of claim 1, wherein thehumidifier wick frame further comprises a connector to removably securethe humidifier wick frame to the humidifier housing.
 8. The humidifierof claim 7, wherein the connector is a bayonet, a thread, a friction-fitsurface or a pin.
 9. The humidifier of claim 1, wherein the humidifierwick frame and the humidifier wick are separable from one another toallow for disposal of the humidifier wick.
 10. The humidifier of claim1, wherein the humidifier wick frame and the humidifier wick are not areseparable from one another such that the humidifier wick frame and thehumidifier are disposable together.
 11. The humidifier of claim 1,further comprising a first filter positioned on the humidifier wickframe upstream of the humidifier wick relative to the flow of air alongthe flow path.
 12. The humidifier of claim 1, further comprising asecond filter positioned on the humidifier wick frame downstream of thehumidifier wick relative to the flow of air along the flow path.
 13. Thehumidifier of claim 1, wherein the humidifier wick frame is chemicallybonded and/or mechanically coupled to the humidifier wick.
 14. Thehumidifier of claim 1, wherein the humidifier wick frame furthercomprises a wick locator configured to locate the humidifier wick frameand the humidifier wick within the humidifier housing.
 15. Thehumidifier of claim 14, wherein the wick locator is a shoulder formed atan end of the humidifier wick frame.
 16. The humidifier of claim 1,further comprising a heating element configured to heat the humidifierwick to vaporise the volume of water into the humidification chamber toadd moisture to the flow of air.
 17. The humidifier of claim 16, whereinthe humidifier wick frame is configured to maintain the humidifier wickin thermal contact with the heating element.
 18. The humidifier of claim16, wherein the humidifier wick frame and the humidifier wick are atleast partially surrounded by the heating element.
 19. The humidifier ofclaim 16, wherein the humidifier wick frame is configured to maintainthe humidifier wick in direct contact with the heating element.
 20. Thehumidifier of claim 16, wherein the humidifier wick comprises a heatedregion positioned proximate to the heating element and an unheatedregion that is spaced from the heating element.
 21. The humidifier ofclaim 1, wherein the humidifier wick frame further comprises an air flowbaffle configured to lengthen at least a portion of the flow path forthe flow of air through the humidification chamber.
 22. The humidifierof claim 21, wherein the air flow baffle is helical in shape.
 23. Thehumidifier of claim 1, wherein the humidifier wick comprises one or moreof: paper, hydrophilic fibres, and cellulose fibres.
 24. The humidifierof claim 1, further comprising; a reservoir configured to retain anadditional volume of water; and a delivery mechanism configured todeliver a flow of water from the reservoir to the humidifier wick. 25.The humidifier of claim 1, wherein the humidifier wick is shaped tosurround at least a portion of the flow path.
 26. A respiratory pressuretherapy system comprising: the humidifier of claim 1; and a respiratorypressure therapy device configured to pressurize the flow of air tobetween 4 and 30 cmH₂O and direct the flow of air to the humidifier.